How many 1935 pennies were artificially darkened with hypo?

[secret santa 2,016]

We're only talking of those that survived rather than those struck - there may have been several of these different anomalies which have got lost over the years.

[1949threepence 3,366]

20 minutes ago, secret santa said:

We're only talking of those that survived rather than those struck - there may have been several of these different anomalies which have got lost over the years.

Yes, I did wonder that myself. But I'm trying to envisage the possible production scenarios. In the case of the 1932 mint toning, there is no plausible way this could have occurred without operator knowledge, as it requires separate intentional intervention. So how many and why no record? 

The only inadvertent way that the 1932 pennies might have been mint toned, is if some other coin blanks intended for different coinage had already been so treated, and for whatever reason found their way into the penny blanks. Although the one apparent discovery is exactly the same size as the standard penny.    

In the case of the non standard metal pennies, again it's difficult to envisage a situation in which an entire batch could be minted and distributed out for circulation, without somebody realising what had happened. Although if an incorrect sheet or sheets of metal were accidentally inserted into the process, between standard sheets, then I suppose it's possible they slipped under the radar - but it seems odd, to me anyway, that not one other specimen has been discovered.  

I probably shouldn't be so probing, but these type of questions fascinate me - especially on a dull, wet Wednesday afternoon in December.

[Rob 3,002]

My money would be on it being Nickel given the known 1923 & 1924 nickel shillings. Iron or some other ferrous material doesn't give many options. Modern neodymium magnets aside, the only magnetic elemental candidates are Iron, Cobalt & Nickel