This is on the stick of my backhoe, I haven't any idea, other than maybe a finger attachment.
Most likely for a thumb.
thumb
I couldn't remember I knew it was something on a hand, A thumb now that would be handy for clearing the trees off the land I have. I wonder if is was a factory attachment.
I've seen things like post pounders and augers put on bosses like that. What do you have for extra hydraulics?
It doesn't have any extra that I can tell. Apparently at one time there was something attached to the pins welded on the stick, also there is a couple pins further up the stick, which may have been for a ram or something.
Here is a picture of a mechanical/fixed thumb:
Most likely for a thumb. I made a thumb last year for my Yanmar and highly recommend them - makes cleaning up rubbish, trees, scrub etc so easy.