Interesting, The Wiki says up until 1963, didn't know they changed the formula at all. Be interesting to see how well ones from before and after the change held up comparably.
I have a bunch of the very early ones, the differences with early ABS are:
- changed shape slightly, some warping
- the colours faded
- they became quite transparent
- they don't bind at all or very very loose
The early ABS ones are about as good as new other than being dirty and a couple of scratches. No discolouration, they bind just fine, no warping as far as I can measure.
Cool, they must have had some great QC with the ABS to do that well for so very very long. I'd love to see the acetate ones in a picture if they went transparent, that's a really neat "failure" mode.
