TanksThe 33 and S are what are commonly thought of and described as "workers marks"; they meant something to someone-perhaps the assembler- at one time-but have no
other particular meaning.
tanksin addition to what Don said - hidden markings are the makers marks, i.e. not a proof or acceptances, so, impossible to know.
The exterior 'S' might mean something, but on Mauser, not a DWM part.