Going back and checking my 2 butt plate side by side pics, they are different for sure.
The one with the knob has a lot more space for adjusting the plate up and down.
The one with just the screws is a lot smaller and is most likely stock as the slotted screws match everything else. This is also what Stew has on his much revered snare :)
Hopefully picking up in hand from Goodwill later this morning a Pearl snare that has the knob style butt and getting a COB Pearl by Sunday USPS sometime today to inspect the non knob butt :)