History Behind the Steel Pan Seat w/ Holes

So I was browsing numerous pictures I have saved off the net and taken at shows and a spark of curiosity came upon me. Of the pictures I viewed, many of the ZT, ZA, ZB, & RT series tractors had the stamped steel pan seats with holes in them, no padding whatsoever. However, there seemed to be 3 different kinds of seats. The first was a 24-hole pan, having a shallow middle (crotch area) and slightly raised sides. Then there were a 3-hole and what looked to be an 8 or 9-hole seat with a more pronounced middle and raised sides.

Now I have seen the 24-hole seats on many different implements, mostly horse drawn, but have seen them painted every color under the sun as well. You can even get them through reproduction part suppliers all over the net.

With that being said, is there truly any breakdown as to which ones are original, if MM ever assigned an official part number to either of them, or what models they were used on? Was it a scenario of MM used what they had at the time or are the originals long gone and what I have seen are just basic replacements?

Thanks for viewing. This is just a post of curiosity to gain more info on this great line of machines. Thanks!

I beleive the more flat looking seat with many holes was used up through 1937. 1938 through around 1940 or so used a deeper dished pan with about 9 holes. The 3 hole seat, with the exception of the flat-back cushion seats used from 1948 to early 1950, was used from the early forties through 1955(1958 on the GB's & some late UTS versions). Keep in mind that the deluxe cushion seats were also available as an option starting in 1938, but not too many were actually equipped with them early on.

This is not gospel, as nothing is with M-M, but should be pretty close I feel.