I feel like there is a subtle differences between a one arm razor and just a razor (?) patterns?...just an assessment from seeing plethora of pics on the forums...
The regular razor pattern's 'hook' is hardly a hook with the pointy part basically tapered off like the back of a spey blade (like the case pattern shown above). I have the regular razor patterns in my possession and I've 'attempted' opening it one hand by 'hooking' it on the side seam of my jeans. Near impossible. The hook just won't grab easily unless I wore non-stretch, blood stopping tight jeans lol. Even then, it takes a considerable force to be able to press into the material for it to grab and open...only my opinion...
The One-arm razor (like GEC one arm) pattern on the other hand, at least ones I've seen, has a pronounced point (not tapered) that almost pokes into the material you are wearing.
Regardless, what do I know, I've also seen plenty of 'one-arm razor' patterns advertised that has the tapered hook...
Just an observation!