Ventometers And Their Use And What For

I have before me a ventometer of which I know nothing.

The only markings are a name of -W.Gregory & Co London-

It is the one pictured in the bottom right of the picture below--borrowed from Mr wheatfields posting.
https://www.milsurps.com/images/impo...Ventomr5-1.jpg


So a few questions--
a) anyone have instructions (printed)
b) anyone have instructions on how to use this ventometer from personal experience, how to mount how to use.
c) what will it fit ? A Martini or a Lee Enfield (long lee)?

Regards
Terry in Victoria

See if this helps

Ventometer

What will it fit? any of the rifles mentioned plus a Snider.;)
You could even use it on a P53 rifled musket though that is most likely a bit early.

It doesn't "fit" anything, it's just used as a guide to mark the rifle sight for windage.