does anyone know of a good resource on detecting cast counterfeits? I know there is a book on detecting counterfeits, and I have not read that yet. If anyone out there has read this book, would you recommend it to others? I see a lot of people commenting on various signs - bubbles, lines, surface appearance. I see it when people point them out to me, but they often escape my notice before that.
When casting is suspected - or when the coin being examined is a known target of casters - that's the time to put the 10X or stronger loupe on the fields.
On unreeded coins the edges can be telling, but the most important places to look are the flat fields. On a struck coin there are generally flow lines visible, especially under high magnification. On cast coins there will be no flow lines, and unless they have been individually smoothed and polished, they have a grainy surface. The area above "IN GOD WE TRUST" in the first posting, and aound the "JM" in the fourth posting of >>this thread<< are clear examples. It's the post-casting polishing that eliminates grainyness on cast bronze figures and statues.
that was the thread that prompted me to create this one. on the third photo in the second posting, I could see clearly that the flat surface 'looked wrong'. it was clearly odd. From the first post, I knew it was fake because of the type and year, but most copies, unfortunately, are not so clearly wrong. In this thread: http://www.cointalk.org/thread6332-grading-older-mexican-reales-coins-(1730-1905).html Doug mentions 'casting bubbles', and I should have asked at the time, but I didn't. I don't know what that is, nor where he spotted them. Since this is the type I collect, I think it is essential, to me, to be able to spot such indication... Like I said, I should have asked when I first read this post a while back.
Cast coins will often have pits on their surface from air bubbles that formed during the casting process. Absence of these pits is not a diagnostic though, as some casting methods do not produce the bubbles. And, pitting can often occur on older coins and appear like the pits from air bubbles. Usually this would be but one sign, or indication, that the coin may be cast. In the original thread it was said best that there appeared to be casting bubbles and the coin would have to be seen in person to determine whether or not the coin was genuine.
Take a look at this coin from that post. 1765 2 reales Look at the area above the crown and below QUE - see those little dark spots ? Then look on the left around VTRA - more dark spots. And more around the date. Now most of the spots are circular - just like a bubble is when it rises to the surface and pops. Then the pit left by the bubble fills in with dirt & grime over the years and they become darker than the fields around them. The surface of a cast coin can also appear bumpy and irregular instead of smooth as on a struck coin. And while you will seldom see it in a picture, if you closely examine the edge of a cast coin you can often find the injection port - or hole where the metal was poured or injected in the casting mold. This is usually a round hole as well and will quite often not be flush with the surface around it.
I do see those, and a couple more around the o in the mint mark. So the pit left behind is what to look for in this example, and the pit would have a lip around it like one would expect to be left around after a bubble in a metal rises to the surface and pops? I've never seen that - I have some chinese counterfeit cash coins. I'm going to check the surfaces and see if I spot this sort of thing. Thanks!
