Could be part of the sn, could be an assembly code, could be a date code, could be part of model designation
Long Barreled Pistol
Could be part of the caliber marking
30 caliber with 30 grains of powder
9mm IS the caliber. If you mean what is it equivalent to, it is approximately the same as a .38.
The marking of the nickel steel barrel meant that the rifle could be fired with smokeless powder.This powder created more pressure than black powder.
Platinum
peanut butter
375 is the marking for 9 carat gold. Usually vintage European will have this marking.
Caliber is the diameter of the bore of a firearm. It's expressed in hundredths or thousandths of an inch, as in .45 caliber or .380 caliber. Curiously, the actual diameter of a .38 caliber slug is 0.357 inch.
It denotes a type of 30 caliber ammunition adopted by the Military in 1906.
The term caliber is often used to mean "level of excellence." If someone uses this phrase, they mean he was a good employee.
the caliber or gauge