Restoration – A Steep Learning Curve


Let me start by disappointing everyone looking for free tips and how-to’s. You won’t find them here; save yourself some reading. The reasons for this should be obvious:

  1. TEC won’t be held liable for greedy and ignorant novice restorers attempting to learn the art on key date coins. It’s well known that the collecting industry is full of unscrupulous dealers and collectors. Enough coins have already been destroyed in the name of profit.
  2. I’m going to show readers some shockers in this post. This is to deter amateurs from rushing out and purchasing dangerous chemicals and to highlight the extensive (expensive) pains experienced in learning some basic restoration skills. Why would any professional give that sort of bread-and-butter information away for free?

A less obvious reason is that I have been guided by curiosity my whole life. School was a prison of theoretical boredom and chemistry was no exception. Now that I have a reason to learn the basics of chemistry and metallurgy I am absolutely fascinated by the processes. It’s why you’ll see this author bang on about toning aka Thin Film Interference. I suspect that genuinely curious collectors will be able to pick up hints from the various writings on this subject made by TEC and begin to experiment themselves – I’m fine with helping those that want to help themselves.

A basic understanding of metallurgy in the creation of bronze alloy permits a more realistic appraisal of coins that TPG’s like PCGS wipe their hands off with “altered surface” and “suspect color”. Here’s an example of that learning curve in this KGV obverse. What do reader’s see below? Feedback invited in comments at end of post.

1934 obverse comparison

Compare the die markers on these two coins. What do you see? Why?

Restoration – Driven By Curiosity

Here’s a $600 learning lesson in fakes and restoration. I purchased the cast Centenary florin for $20. At the time I had little concrete reason to really dig into the details of its manufacturing. That was, until I restored the 1945 double struck penny on the right (purchased on Ebay of course!). Note the bubbling on the detail of the off-struck roo and legend detail in AUSTRALIA. Those details were not evident when the coin was purchased as the surface had an even coating of dust and dirt.

Once the coin had been restored, those details pinged off a memory of the centenary florin and voila!, A = B = likely cast fake die striking said penny. This author has no rhythm or rhyme in the acquisition of learning. It’s simply a matter of more material arriving on my desk for inspection and connections are made after a little introspection and comparative studies. It was a similar issue for the KGV penny above left; eventually identified via a business strike on the right. Given that Uni post-graduate certificates are being quoted at $15k today, I believe $600 for this lesson was a good deal!

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Restoration Requires Honesty and Transparency

Now you might think the author a sadomasochist for paying $650 (from Ebay… duh!) for the 1944 double struck Penny below, but the access and learning exposure I got from one of the world’s leading experts on errors (Mike Diamond from makes this a relative bargain. The previously posted article below elaborates on the conversation that was had with Mike. A common refrain from those who believe they hold a rare error of extreme value is that they cannot believe when they are told otherwise. Many people cannot accept responsibility for their actions; like spending $650 on another Ebay fake (guilty!).

I’ve pumped Mike time and again (respectfully and patiently) for his understanding, so that after a couple of coins I’ve ceased making these rookie errors. For the penny below it is in the “probably fake” bin, but I await to see other examples that arise in future in order to make a better determination. What TEC doesn’t do is flog these coins on others to make it their mistake. That’s unethical.

Restoration – The Good, The Bad and The Ugly

The Ugly

Probably not the best coin to start learning restoration on. A PCGS XF40 graded Double Dot 1920 penny sets the collector back $400 in the present market. However this one was riddled with corrosion and returned by the buyer who understood that verdigris cancer is the death knell for a bronze coin. Unfortunately PCGS are not good at restoring bronze and quite frankly, neither am I at this sort of level of corruption. This coin awaits further techniques that will be practiced and refined in the near future, so as to complete this restoration.

1920 double dot penny partially restored

A coin awaiting further restoration, once skills have been acquired to continue.

The Good

In contrast to the above, an UNC coin that’s been well looked after requires just a minimal degrease and a protective coating of Verdi-Chem. The value of this coin has definitely increased. Very aesthetically pleasing. The 48 Penny returns to a collector. TEC has a restored 51 high lip for the collector of bronze errors (see below)

1948 High Lip

UNC stiff collar error creating a high lip – a lovely coin to restore


The Bad

Ever had the best intentions and forgotten to follow it up? (go on, be honest with yourself). That’s what happened to this Quarter Anna after letting the jar of acetone dry out. I’ve not yet found cheap but perfectly air tight sealed jars for pure acetone – it’s a highly volatile precursor chemical used in manufacturing methamphetamines (don’t even think about it). I have a fan blowing over the table when I work with this stuff as I don’t want to end up like Steve Jobs. I don’t stick my fingers in this crap either – gloves or a brush/cotton bud to slide the coin out of the jar. I’m holding onto it to observe the corrosion taking place and will attempt to reverse the damage to see if it’s actually possible when I have a spare moment.

Letting a coin soaking in acetone dry out in the jar after forgetting about it

The Secret TEC uses in Restoration

Remember that in today’s online marketplace, buyers must be able to see the error in an image and make a determination on the basis of that image. This 1961 incuse error penny was given only a coating of Verdi-Chem. Why? Because grime creates contrast! If this coin had been degreased, the ability to see the error becomes so much more difficult.

1961 Incuse Err


To illustrate the coin’s surface, depth of field is advantageous. This author returned to photography just as Micro four-thirds was being released by Olympus. To understand the equivalent 35mm lens being used by TEC for numismatic photography, see the following chart. The go-to Olympus lens for numismatics is the 60mm Macro. That is equivalent to a 120mm focal length in the old days. Looots of depth of field.

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But Wait, There’s More!

The small and light 4/3 sensor cameras works quite well racing up and down the basketball courts, especially when combined with the new generation of Zuiko pro lenses shooting at f/1.2! However for numismatics, it’s the hi-res mode that is the bomb. The sensor moves 3 times and takes separate images, to combine in a super-sized raw image. So combined hi-res images with strong depth of field creates OUTSTANDING images that permit collectors to make informed decisions from a photograph. For the nerds and photographers who want to understand more about this technology –

1961 Incuse Error detail

Image detail at 70%


So judicious restoration, combined with an understanding of aesthetics and macro photography all go into TEC’s restoration work. The image above has been compressed by TEC’s site server. The image that customers can download from Google Drive upon return of their restored coins will be full resolution.

Restoration – A Steep Learning Curve That Begins to Pay Off!

TEC is presently offering restoration at $20 per coin, subject to visual inspection and feedback. If it cannot be restored with present understanding, the coin will be sent back free of charge and the collector advised when such restoration is available. New processes and techniques are being studied so that verdigris can be credibly removed for high value copper coins. TEC won’t be hurried on this subject.

TEC can provide significant added value to silver pre-decimal coins already. Take the Centenary Florin below as an example. One of the “special strike” dies quickly created by the Melbourne Mint during the centenary celebrations. This type II proof-like was purchased at auction. It sat in the drawer for several years as PVC damage was eating into the metal (the blackened area). Now restored and graded by PCGS as MS66. Approx. value $5000-$7000. Click on the image to see the PCGS certificate.

PVC damaged Type 2 proof-like Centenary Florin

PVC damaged Type II proof-like Centenary Florin. Now graded MS66. Click on image to see PCGS Cert. Opens in separate tab.

There’s an acute need to protect thousands of Australian bronze and silver coins from further damage, if they’re to be passed onto the next generation of collectors. That’s a skill worth learning and refining.