Obviously a windgauge

It fits on the Martini and Long tom perfectly sleeve as shown

It is marked BSA and has a knurled, numbered knob so as to adjust for repetable windage
Moderator: joseyclosey
Well of course Douglas; just send me your postal details, an as yet undetermined sum of money for postage and packing and of course your bank details, no problemsSo I guessed right!!! Wasn't the prize if you guess what it is you get it ?