S Mint Bonanza (i Know You Like These Gb)

[Zincoln]

5 hours ago, GB_Amateur said:

Hasn't the 1909-S Lincoln alone antagonized me enough for one day??  😉  Very pretty key/semi-key IHC.  I wish even one of my IHC's (all common date finds so far 😞) looked that nice.  But, yes, the IHC's and some early Lincolns, probably because of their tin content, tend to hold up better in the ground than the later Wheaties and 95% copper Memorials.

 

You know GB, they don't seem to publish much that shows the content differences between early and later wheats.  It's quite evident however.  Seems somewhere mid 30's they changed the recipe slightly, as the older dates hold up so much better.  And then, the late war years hold up terribly....used brass from WW2 was a large part of the content from my understanding.  Obviously not from the battlefield, but likely from training activities.

 

Sorry to antagonize!  I'll pull back on the throttle😄

Brian

 

[GB_Amateur]

7 minutes ago, Zincoln said:

You know GB, they don't seem to publish much that shows the content differences between early and later wheats.  It's quite evident however.  Seems somewhere mid 30's they changed the recipe slightly, as the older dates hold up so much better.  And then, the late war years hold up terribly....used brass from WW2 was a large part of the content from my understanding.  Obviously not from the battlefield, but likely from training activities.

Interesting that you bring that up, Brian.  I did a rather extensive study (find it here) a year ago on Indian Head and 95% copper Lincoln Cents and their variation in VDI with time (even with a short part on what being in the ground for a long time does to VDI).  I also reported on what I think is the best available info on composition variation (which as you note is incomplete).  It would be nice to be able to do X-Ray Fluorescence Spectrometry (XRFS) on cents but even the lowest cost versions of those are way outside my budget and it might take a much more expensive version to really sort out tin content.

My claim that tin content, even small changes, can affect the corrosiveness is somewhat backed up by mint records but more extensive investigation (e.g. with the above mentioned XRFS) would be much better.

[Zincoln]

6 hours ago, GB_Amateur said:

Interesting that you bring that up, Brian.  I did a rather extensive study (find it here) a year ago on Indian Head and 95% copper Lincoln Cents and their variation in VDI with time (even with a short part on what being in the ground for a long time does to VDI).  I also reported on what I think is the best available info on composition variation (which as you note is incomplete).  It would be nice to be able to do X-Ray Fluorescence Spectrometry (XRFS) on cents but even the lowest cost versions of those are way outside my budget and it might take a much more expensive version to really sort out tin content.

My claim that tin content, even small changes, can affect the corrosiveness is somewhat backed up by mint records but more extensive investigation (e.g. with the above mentioned XRFS) would be much better.

I read your report, and all i can say is WOW!  I'm an engineer and i too like detail, but you were on a mission!

Very interesting, and I have to say I have no reason to disagree with any of your conclusions.  Quite a few head scratchers that might be answered with enough access to mint records, but I digress. I too am left to conclude that your tin/zinc mix hypothesis likely answers the question of why earlier coins held up better....though i must say many of my late 30's and early 40's dates don't hold up as well as those prior to say 36.  Not sure why as the comp wasn't changed until the war (if i recall your data correctly).

I think you are likely spot on with early wheats potentially using IHC planchets.  They certainly had placed large orders, and when they didn't produce many IHC's in SF, they almost certainly used those planchets for the Lincoln cents.  As early mintage was low for 1908s and 1909s IHCs, and for 1909s, 1910s, 1911s, etc wheats, it's easy to see how this may have occurred.

Now, if only my chemistry and materials science courses could tell me how that tin/zinc indeterminant mix yielded a hardier coin when exposed to certain environmental factors...and those at least here on the west coast that get a very nice deep green verdigris in our wetter climates.  Our desert areas aren't that wet, and they don't react the same.  And after the early 30's, they also seem to react the same...more deterioration than green verdigris. 

All I know from observing our current Zincolns is that it must not be the zinc that is the helpful element😆

Oh, the unanswered questions!

Zincoln

[Tom_in_CA]

Good show !