Modified M2A1 Ammunition Bag

[19thinfantryregt]

I have a M2A1 Ammunition Bag that has been modified into a backpack at some time. After doing a quick Internet search, most info I find on the M2A1 shows it as the vest configuration. I did see one or two photos showing the same pack as mine but nothing more.

s18.photobucket.com/albums/b107/WBAirborne/M2A1%20Ammunition%20Bag/

Any thoughts?