LAST EDITED ON Dec-14-15 AT 10:30 PM (EST)
 
I think you're right about that compartment in the stock, my Garand has a similar setup to hold a small cleaning kit and grease jar.

Oddly enough the stripper clip hung on a lot longer than I'd have though practical. The Springfield M1A (clone of the M-14) still has a stripper clip guide machined into the receiver. Apparently one of the major gripes about the Garand was it wasn't possible to top off a partially used clip, so the its successor remedied the problem.

Nicely done on this article too, I hadn't known the SMLE had a detachable mag. Though it seems so typical that it was designed in and manufactured without ever being allowed to be used as intended.