I happened to be looking in my old brass and came across one that was marked as RFM- UMC intead of REM-UMC.Was this a tooling problem and how common was it.
I also just counted my collection and I have 150
different cartridges not including duplicates.
It ranges from the .14 jones rimfire to the .460 Weatherby.Below I list a few of my favorites.

350 Griffin & Howe
30 Newton
280 Ross
7x61 Sharpe & Hart Super
22-3000 Griffin & Howe
30 cal 1903
and the 9.3x74R
just to name a few.

I can't wait till the next cartridge to come to my area.

The headstamp bunters used in the loading processes wear out after a few zillion stampings , and I suggest that your example escaped detection in the quality control inspection process . They cant look at every single case , but usually defects are detected fairly promply .
These sort of variations are collectable too , makes for yet another variation in the collection .

'Course you could always start collecting headstamp bunters but they are a reasonably scarce item outside of the ammo factory .

muzza thanks again I only have 1 of these.
you must be a long time collector.I have been doing this since i was a kid and just recently got into the shows I was baffeled at what is out there that I did'nt know even existed.
And from there the free and common ones I have.And is now a bit expensive for some.I believe a
person could spend $10,000 and still not have
everything out there.But one would have an a
very extensive collection!!

cal30, one could drop ten grand on just two or three rounds if they were of a mind to do so! There are likely almost as many variations in cartridges as there are in coins minted since the introduction of fixed ammunition - perhaps more!

I suppose a person could.
But my money takes to long to earn
to be in those ranks.