The hard rubber seat for the 102 did not flip up like the fiberglass pan seat on the 122/123 and on the 1x4/5 series. I've not heard of one of the hard rubber seats being original to a 122 or 123. I suppose there's always a chance that they ran short of the fiberglass ones and/or someone at <FONT COLOR="ff0000">I</FONT><FONT COLOR="000000">H</FONT> goofed and put one on a 122.
It's really odd to hear of one on a 72. That I believe must have been done by a PO at some point during the past 40 years.