Here's pics of the three I have wce. First one is a 1970's mid arch catcher, second one is one I had scavenged off a1970's VC-Mustang and replaced a missing one on this 1980s yellow Vortex catcher and the last one is a 1980s Powertorque thumb latch catcher original AFAIK. All the same design as yours, apart from the colour.

NormK, at least that relates to the plastic used on Victa catchers. I cut open a 1980s SPFC Mustang thumb latch catcher and was surprised how thick the plastic is (about 4mm) and yet they were so prone to cracking.
I expected it to be way thinner.

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IMG_20200624_212728-1000x564.jpg (24.15 KB, 54 downloads)
IMG_20200624_212954-1000x564.jpg (29.91 KB, 53 downloads)
IMG_20200624_213504-1000x564.jpg (35.25 KB, 53 downloads)
IMG_20200621_170303-1000x564.jpg (120.41 KB, 52 downloads)

Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!