https://youtu.be/cNrHAjkr-vo

As far as I can tell it is a m1956 butt pack was a back pack and the side pack was a variant one.

The Alice system did not come into play until the mid 70s so most likely the m1961 designs were probably used as a base.

The video is chock full of historical information and provides the names of all the various pieces so close looking surplus items can be more easily located.

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The impossible takes a while longer and goes over budget too...