The site just ate my first reply - so I will try again.
What aspects identify this coin as contemporary rather than a more modern (1960-1970's) forgery?
This is a somewhat difficult question to answer. When I looked at the coin - it struck me as a circulating type. To figure out why I had that impression I had to study the coin and my methodology both. I would say that it is based on experience with hunting for counterfeits but I feel I can outline the process that I employ.
There are two questions a fake raises. First and easiest is spotting the fake as NOT REAL. Most everyone gets that part. The far more difficult part is how to estimate when a fake was created and for what purpose it was made.
Here you need to know how forgers think and what motivates them both now and in the past.
To ID a contemporary counterfeit you need to examine where an individual counterfeit best fits into the types of fakes that were made. I study each coin to make sure it MAKES sense and falls into a logical place on the continuum of forgery.
So here we have a very well worn coin that uses a fantasy design and appears to be struck. The wear does not look artificial. The coin shows a deep impression of the edge design which intrudes into the dentils. The coin itself is struck on a solid metal planchet which exhibits poor color and patina for 900 fine silver.
So from here - I look at the issue of condition. The coin is too low grade for a numismatic forger to have created it as it is. Also most numismatic forgers (even in the 1950s)would use a transfer design that would not be as bad as this and the coin absolutely would be higher in grade to attract "the mark". So to me it makes little sense as a Numismatic forgery. In the 1950s or 60s the value of such a worn common coin was extremely low. The only way around that is to postulate artificial wear - for which I see no evidence.
Next I think about where this condition coin would fit better. A contemporary counterfeit is often made worn to attract no attention. In the case of a contemporary counterfeit the edge design would be critical because merchants and bankers stacked coins and no edge or a weak edge attracted unwanted attention. Here the deeply set edge on a coin so well worn makes more sense as a contemporary counterfeit. An actual coin in circulation should have lost nearly all the edge design by this point of wear.
Another issue is the design used. The coin is a fantasy design that makes several VERY simple errors that would be noticed by even a novice collector - the HIGH superscript on the Ms for example. Also the incorrect alphanumerical fonts like the 7 6 and 8 all of which are terrible. That is not what numismatic forgers do normally. They use transfer images that are faithful to the design. Here the fantasy design with errors fits only as a contemporary. The design is completely logical for a CCC Class 1 but totally wrong for a NF Class 3.
Finally the nature of the metal. The color looks to me like a very old patina on a low grade
silver coin. When this coin circulated - Sheffield Plate was NOT yet used widely for forgery. So a layered coin would most likely be later or the edge covering would be a VERY early form and I do not see that. CCC's in 1775 were either cast or struck. Transfer image dies were NOT yet possible so struck copies were made from engraved dies. The era of the forgery as Class 1 fits the available technology for that time.
Finally very early (successful) counterfeits tended to contain significant amounts of silver which is why they are so darned rare today. People knew the heft and dimensions of a silver coin and could recognize the ring. Cheap tinned copies did not fair well. However, a high silver content fake DID succeed and on more than one occasion. Look to Riddell for average assays and see what I mean. A counterfeiter could profit handsomely from a 60-70% silver coin because the 20-30% shortage was worth pursuing. At the same time a 60-70% silver dollar would have been worth melting - and we know from Riddell's work that high average silver contents predominated into the Federalist era. Debased silver did not re-appear until numismatic forgeries began to appear but in that context - transfer technology predominates.
What I am saying is that the forensic evidence that I see for this coin makes me believe that it will be contemporary. It would be anomalous as a numismatic forgery. A silver contemporary counterfeit (Class 2) was never made.
I hope that helps. Follow the thought process and use logic. All coins even bogus ones EXIST FOR A REASON - match the clues to a reason and you get a date in most cases.
My book on Counterfeit Portrait 8Rs is available from Amazon http://ccfgo.com/TheUnrealReales
or from me directly if you want it signed.