I Did a little digging in the old reg pile this morning and came up with some good info. I have 3 different models of HW seconds, a Scuba Star, a Scuba Star TDOK and a Scubair. All 3 appear to use the same diaphragm (or at least that was what was in them) although the manual says differently. In addition I found a loose diaphragm that appears to be a later, more modern design but it fits perfectly into all 3 and is made of a softer material (rubber, silicone ??) The old version had metal pads on both sides riveted together as opposed to one bonded/glued into the new version. The metal pad on the new version was slightly bigger but that shouldn't be an issue.
It would take some testing but I think the later example I have might be worth looking into.
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