Personally have never seen or heard of another, so quite a rare piece. It looks very much like WWI era German scopes. The "Britishicon Made" engraving would suggest it dates to the 1920s. As most scopes were German in origin pre and post WWI, I suspect that was put on to assure potential customers that it was indeed British made and not just a re-marked German scope; understandable given the feelings of the time. Several British retailers and gunsmiths did sell re-marked German scopes before WWI and scopes were generally associated with Germanyicon in the mind of shooters being so commonly used there and so much used in WWI.

The adjustable range scale resembles military types. The rings are Parker-Hale I assume?

I wonder if Ottoway decided to take a stab at making a scope after WWI, when they probably had a great deal of surplus capacity left over from the war and probably quite a lot of surplus lenses etc.

Aldis did the same thing and were still trying to flog a poor variant of their No3 scope from WWI in the 1950s! Sadly, the optical quality was not as good as the original, nor was the adjustment mechanism and the whole thing was 40 years out of date. A rather sad end considering that the optical and mechanical quality of their scopes in WWI was really superb.