Whats this used for?

Made by Pachmayr

Attachment 217159. Attachment 217160

look up the patent

but appears to go on sideplate of something...for sights of some sort perhaps???

Lower part of a "Lo swing" scope mount (missing the rings).

@NZShoota any chance of a photo of entire unit????

Just Google "pachmayr lo swing mount", and some pics should show come up.

yip that works...looks like it was a good bit of kit back in the day.

Had one on a Mini 14 in the olden days.

Be handy for bush hunting on rainy days.