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Overlay experts - seeking your help - I keep getting an error
Overlay experts - seeking your help - I keep getting an error
Overlay experts - would one of you overlay a 1912 Lincoln Cent obverse onto a 1910 Lincoln Cent obverse? Post an image of the entire obverse overlay then crop it and post an image showing only the date. When I attempt it - I keep getting a deviation I am not comfortable with.
The 1st image presented is a CAD tracing of a Lincoln cent Obverse absent of the Date. I overlaid this drawing onto an image of a 1909, 1910, 1911, 1912, 1913, 1914, 1915 and 1916 proof coins. Then plotted in the date for each coin creating an CAD obverse rendering for each separate coin.
I took these Cad renderings and started overlaying them onto each other. Being that it is generally recognized that the "19" of the date was an element included as part of the galvano; I expected the deviation in location of these two digits from date to date to be minimal. But the overlay of 1912 onto 1910 exhibited significant deviation. That overlay is presented as image two in this post. The date was extracted from this overlay and is presented in image three.
As I continued with the overlays two separate groups appeared to form. Those obverse that matched 1910 (1909, 1911, 1913, 1915) and those obverses that appeared to match 1912 (1914 and 1916). The different groupings are shown in images four and five.
I am fairly confident this deviation is due to an error on my part and was looking for someone else to perform an overlay to confirm it.
Wow, that is impressive and is great for comparison.
Thanks but at the moment I am not sure it is that impressive or great for comparison. I know I am dealing with shadow artifacts on images, camera angle plus strike, hubbing and engraving issues from die to die and year to year but with the "19" originating from the galvano - the deviation (shift in location of the digits) indicated in the red box of the attached image is way beyond any tolerances I was expecting and comfortable with.
That can be explained by different master dies for the 19... Not all will be exactly the same (I have no idea how many masters were created tho)... The last two digits could represent a different individual punching the numbers on... Hope that helps a little!!!
Jim (A.K.A. Elmer Fudd) Be verwy verwy quiet... I'm hunting coins!!! Good Hunting!!!
That can be explained by different master dies for the 19... Not all will be exactly the same (I have no idea how many masters were created tho)... The last two digits could represent a different individual punching the numbers on... Hope that helps a little!!!
But with the "19" of the date originating from the galvano these design elements are transferred to the Foundation Hub during the reduction process. This hub is the origin design for all master dies.
But with the "19" of the date originating from the galvano these design elements are transferred to the Foundation Hub during the reduction process. This hub is the origin design for all master dies.
How many different foundation hubs are made with how many different galvanos... I have seen a show (Science Channel I believe) on how the mint makes coins... There were several reduction lathes creating dies at the same time??? Wexler shows some of them here http://doubleddie.com/58201.html
Jim (A.K.A. Elmer Fudd) Be verwy verwy quiet... I'm hunting coins!!! Good Hunting!!!
....... There were several reduction lathes creating dies at the same time??? Wexler shows some of them here http://doubleddie.com/58201.html
Quote from Wexler's link above-
"The French Portrait Lathe was a reduction tool that traced out the design on the galvano and engraved that design onto the face of a Master Hub. This process was a slow and tedious one taking anywhere from a day and a half to two days to complete the transfer of the design to the master hub. When finished, the master hub had the design in relief and the face of the master hub was the exact size of the coins that would ultimately be produced with that design.
The master hub could be used over a period of several years since it did not contain the date. Each year it would be used to make a master die for that year. That master die would then in turn be used to make working hubs and the working hubs would be used to make the working dies as in the process described earlier. The remaining design elements would be punched or engraved into the individual working dies."
"The French Portrait Lathe was a reduction tool that traced out the design on the galvano and engraved that design onto the face of a Master Hub. This process was a slow and tedious one taking anywhere from a day and a half to two days to complete the transfer of the design to the master hub. When finished, the master hub had the design in relief and the face of the master hub was the exact size of the coins that would ultimately be produced with that design.
The master hub could be used over a period of several years since it did not contain the date. Each year it would be used to make a master die for that year. That master die would then in turn be used to make working hubs and the working hubs would be used to make the working dies as in the process described earlier. The remaining design elements would be punched or engraved into the individual working dies."
If those in the pics were all the same designs then there were several master hubs created??? Since the dates were put on the dies at a later time that would explain the difference in location of the numbers!!!
Jim (A.K.A. Elmer Fudd) Be verwy verwy quiet... I'm hunting coins!!! Good Hunting!!!
If those in the pics were all the same designs then there were several master hubs created??? Since the dates were put on the dies at a later time that would explain the difference in location of the numbers!!!
Those images in the article were from 1998(?). Was the date applied with a "punch" for each numeral (like applying a mint mark then) or was it carved into the master after it was created using the galvano?
I agree but it would be hard to know if the process changed any from, say 1909, where the mint has almost 90 years until the first two digits would have to changed.
The following is newbie speculation_ ....... The first two digits may have been part of the design on the galvano(?) back in 1909. This scenario would make sense from an efficiency standpoint. This would account for the 19 being consistently placed year to year.
Also there may have been a "jig" when applying the date to the master (or was it carved into the master?). That would keep the first two consistantly spaced/placed. The placement of the 3rd and 4rth digits could theoretically move slightly, even in a "jig', if the 1 was inverted and the numeral was not perfectly centered in the metal "punch".
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