If they are the blue plastic with "clear" inserts, I have several of them. We
were given two types of crew checklists - one that was heavy stock with yellow
pages outlining checklist items for various situations as well as a few misc
info cards. The older type was different forms of a basic blue checklist
binder with clear insert sheets (that never seemed to stay clear for very long)
for all of the same info. They came with snap rings but eventually those were
outlawed as they were a FOD hazard - when zip ties came along, they provided a
perfect substitute. I have a few different ones that go back through the
sixties - not sure what was used prior to that.

v/r
Gordon
====(A+C====
USN SAR Aircrew

"Got anything on your radar, SENSO?"
"Nothing but my forehead, sir."