splitting hairs
A "pre-39" denotes a 9mm of that style that is VOID of any model number.
Whenever the frames were made is speculation plus or minus a few years. Dwayne Charron (who was "the" entire R&D department as S&W) was the grandaddy of all post war S&W semi-auto pistols.
Also, S&W hardly ever threw anything away that they can sell.
All those steel frames shipped as "MODEL 39", thus, they are not pre-39's no matter how you want to split it. If you'd like to say the frames were manufactured earlier than the series it was released as, so be it.
Further, only those frames were stored, the blank, empty, uncleaned and untrimmed raw frames, save perhaps a few of the X-R&D models that were in progress at the time.
When assembled and produced they had that current year vintage mechanics including the safety lever. Remember that safety lever went through several revisions. The picture I posted has the original "short" definitive, real "Pre-39" safety lever.
The 6x,xxx range steel frames may have a "shorter" safety lever than a 39-2 (maybe not) but the steel frame released and sold do not have "the" 1st model Pre Model number stamped 9mm short safety lever.