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San Francisco Assay Office proof set inventory – August 1971
This table might be of interest to proof set collectors. It is page 1 of an inventory of medals, uncirculated and proof sets on hand at the San Francisco Assay Office during 1971. The NARA files are incomplete, so this page might be one of the more useful.

Notice that proof sets from 1969 remained in inventory, and 1970 sets were being sold long after the official closing date of December 31, 1970.
Totals at bottom of the page are carried forward from earlier pages of the report.
[RG104 E-328 H Box 1 Coin Sales]
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Comments
Did the mint record transfers of dies in the 1870s?
Are there San Fran records of shipment or Carson City records of receipt?
Always thought about it might be interesting to find docs to support to great over mint marks of yesteryear such as the 75 s/cc or the 1900 O/CC.
Were the mint marks put on in philly or at the branches?
Might not be recordings of a die that was prepared but not shipped and then repurposed
11.5$ Southern Dollars, The little “Big Easy” set
The Engraving Dept. kept detailed records of dies made, shipped, returned and destroyed from the time the branch mints opened. After 1854 these became increasingly detailed. However, virtually none of these are known to exist except from some modern records of the 1950s.
Die orders and shipments are routinely found in the correspondence files, especially after 1972. But there are many gaps and missing journal entries.
All dies were prepared and mintmarked at Philadelphia.
If discovered by the engravers, defective dies of any kind were destroyed.
I've tried to find a paper trail regarding 1900 O/CC dies but have located nothing conclusive or good enough to be published.
Some of these back date proof and uncirculated sets might have been sets held as replacement sets, with the "issues" being sets sent out to replace sets that came back in and were destroyed. They used to do that,and probably still do.