My WW1 British issue (Enfield acceptance marks) Winchester A5 still works remarkably well, at least when the light is good although in poor light it is handicapped by the small lenses.
One advantage is that by recording the readings (as per photo) it can be moved from one rifle to another.
In the photo it is on a .303 Mark III Ross 1910 . When I tried to find it recently it took me a while to remember that it was on a .22 SMLE fitted with a Parker-Hale Easifix mount.
Inside of case lid of a WW1 issue A5. Reference to use of open sights in zeroing shows it was originally paired up with a SMLE fitted with Whitehead side mounts.