I figured since we have the M4 archive, we should do it with all major weapon platforms, soi'll start us off with the mp5 family prototypes....
"HK64, the first actual MP5 to be built under what came to be known as Project 64, named for the year the program began."
"First prototype of the MP5K, produced in 1976. The first version of the foregrip was made of wood, and was subsequently reduced in size to aid in concealability. This foregrip was made from wood."
"MP5SD prototype. The SD project began in 1974. Many of the 'waffle' type magazines like the one shown here are marked with 'SD' on them."