There were many styles of seat pans used throughout the Stingray series and good improvements along the way.
The bottom seat pan on this ‘73 has 8 (4 on each side) round semi punch holes on the sides.
The metal lip that is created from these punches grabs the vinyl material and prevents it from pulling out from between the two pans.
I think this style bottom pan may have been used on the late ‘71 and ‘72 seats as well.
Another improvement was the derailleur wheels (jockey pulley, idler wheel) that were first used on the 72-73 Stingray.
These wheels had teeth for a better, more solid performance.
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