Ok, Gents: There seem to be quite a bit confusion about the designation of Scheel seats so here is the rule
Scheel in the period that interests us had basically 5 lines of seats: 100, 200,300 400 and 500 series
The suffix 1 in like 201, 401, 501 refers to seat that have a backrest forward tilt function, in the 101, 301 it just refers to an adjustable backrest.
The suffix S like in 401S refers to the more voluminous backrest upper bolsters
There were others suffixes like 2, 3 or N that referred either to a shape or material used
Hope this helps