This one is not numbered either - but the style and the fact its 531 Pro rather than 653 indicates its likely to be pre 1988. Lo-pros did not come on stream in a big way until about 85 so on that I would guess with the style of the paint for it to be about 1986-7.
Aende dating
This one is not numbered either - but the style and the fact its 531 Pro rather than 653 indicates its likely to be pre 1988. Lo-pros did not come on stream in a big way until about 85 so on that I would guess with the style of the paint for it to be about 1986-7.