I am not 100% certain but I believe the 22 size flip up grates began (originated) with the One Touch Plus models of 1988. As for non flip, anything from the late 50s to prior to 1983-84ish was the old style solid grates with the straightened yet slightly angled handles. Around the 83-84 period the handles were bent inward somewhat. I can get pictures later for comparison. In the 1990s the first thinner grates came out (BAR B KETTLE, later the OTS and now the "Original Kettle") came to be, at first the had the rounded or arched shape handles, by 2010 they resemble the flip up handles only thinner.