I noticed the image in the last E-Sylum depicting women engaged in planchet weight adjusting using files at the US Mint in 1852. I have never seen adjustment marks on any US coinage after the steam press was used in 1837. Is it true that they were still hand-adjusting planchets at the Mint as late as the pre-Civil War years?

I would think we'd still see adjustment mark traces in the blank fields and in the blank areas of the shields' bars. After all, we do often see planchet "drift marks" , grease streaks and laminations on such post-1837 coinage which don't disappear or even start to dissipate under the pressure of a steam press. About three years ago Legend offered a Gem Proof Barber half dollar for sale on their website with "adjustment marks" visible on the Barber Liberty Head cheek ! I emailed them that adjustment marks on such a late coin were impossible and never received a reply.

All gold coin blanks and planchets were adjusted by filing or shaving, as were silver coin blanks for quarters and larger denominations. Improvements in rolling mills and cutting machines between 1836 and 1840 by Franklin Peale, and Mint balances by Joseph Saxton and Peale, resulted in much more uniform blanks and planchets. At this time, all face filing of blanks was abandoned in favor of edge filing. The 1852 illustration depicts adjusters engaged in this operation. This practice ended only with cessation of gold coinage in 1933, and silver during WW-II due to labor shortages.

As a practical matter, the deformation of planchets during striking obliterated most face adjustment marks and all edge adjustment marks. Most surface striations on later 19th century coins resulted from rolling and drawbench manipulations combined with incomplete filling of the die.

[Sources: Journal of Numismatic Research, Spring 2013; the book From Mine to Mint includes extensive descriptions of adjusters and how they did their work.]