HW Cooey SMLE #1 MK IV aperture sight

I have never seen one before and can't remember where I got it. SMLE MK IV .22 rear aperture sight. Canadian CEF item featuring a standard Ross M10 ladder sight with the same .303 graduations.

It is essentially a Ross rear peep grafted onto an adjustable dovetail base, that fits tightly to the LH receiver side of an SMLE#1. Thumbscrew sadly missing but probably a fairly common pitch ? Elevation ladder works smoothly and windage is achieved with the aforementioned dovetail ( five increments marked)  There appears to be a leaf-spring missing  which would be standard M10 part.

LMK if it floats your boat....$ offers or trades seriously considered.