My first Mustang, in fact my first classic American Muscle Car after I sold my FG F6 in 2009 was this Chestnut Metallic (one of only 368 in that colour) 70 Mach 1 M code.
I've since had a couple of other makes and am currently driving a 66 Mercury Cyclone GT 390 4 speed (see avatar) with a time capsule 66 Mercury Park Lane 410 under cover in the shed.
But for my next car, I'll have to come back to a 69 Mach 1 R code.