All About Pocket Knives

I have a 3 1/8" Ulster Knife Co. pen knife that is all original and near mint condition. Both blade tangs are marked "Ulster/Knife/Co." and the back side tang of master blade is marked: "24348".
I have many Ulster Knife Co. knives but none have numbers on them. Some "Ulster Knife" knives do but this is a post 1941 marking, not "Ulster Knife Co."
Anyone else have Ulster Knife Co. knives with numbers on back side tang ?
Thanks, i appreciate the help.
kj

A little less than half of my Ulster Knife Co. knives have pattern numbers stamped on the back tang.

Pattern numbers are in the picture titles.

I just checked about 50 of my "Ulster Knife Co." knives, from big Jacks to 4 blade Senators. None have a pattern number. Note, i am not asking about "Ulster Knife" which is a marking used from 1941 on when owned by Albert Baer. (i think i have this history right)
Why are some marked with pattern numbers and others not ?
Is there an "Ulsterologist" out there who can shed some light on this ?
kj

Very odd.

All of the knives I posted are marked Ulster/Knife/Co.

If you blow up the pictures I think that you can see the actual tang stamps on some of them.