Hughes Simplex Rock Bit Fob Sterling Silver

I was out metal detecting a couple days ago, in Oil City, PA around an old late 1800's-1900's area with an old oil drill well that was located nearby and dug up this fob. At first i thought it was a can opener, but then it is marked sterling. on the back reads: hughes simplex rock bit, hughes tool co. houston, texas. It is very nice looking and clean, as with silver preserves in the ground well. Doing research, and big thanks to AR8Jason, these were offered to high execs or oil business owners and they were supported by a leather strap to keep harnessed. As far as the rarity? I don't know. Something is considered rare for how many and how much someone wants something.