Marlin manufactured ammunition of a short time and would refer to the 38-40 as 38-40 Marlin Safety in advertising. The caliber marking on the top of the barrel where it meets the receiver was usually 38W or 38WCF. I have not heard of "38 Safety" being used.
The top of the receiver would be marked "Marlin Safety". No markings should appear on the upper tang and the serial number should be in front of the trigger guard.
Does the roll stamp on the barrel match what I indicated in previous post?
MM93 is the local expert and will probably know more. If Marlin ever used 38 Safety as a caliber roll stamp he has probably seen it.
Nope, you've covered it all wery well vermntcllr! I've never heard of one marked that way.
Make sure the rest of the rollstamps on the barrel are as vermntcllr listed. If not, it may be a rebarrel, and someone stamped the caliber incorrectly.