I think the early MF10s, 12s, came with pepper top mufflers and the later model 10s, 12s, the deluxe muffler was optional, check out "AGCO parts books" they show both types with serial #s, production dates.
The factory deluxe muffler is a nice feature and there a bit quieter.
Yes, it was listed as an option much like the headlights were. I have one on my 12G and when I get ready to re-work the 12H with the OH140 motor, I will be custom building a muffler just like it. I am really thinking that I may buy a sheet of stainless, build a jig to drill the holes, and fold it on a brake. Either way, that style muffler will be used, it's night and day quieter than my neighbors 12G. That said, there should not be any "year range" that had them, but there could be a starting point when they started to sell them.
I have only seen the deluxe muffler on the later models. My guess is that it wasn't available, or at least common, until after 1970? I had one, but it broke internally. I now use a similar Nelson from a JD.