Dan, The hook buttplates I have seen were aluminum. The buttplate in the photo I mentioned appears to be aluminum. In the text I have found mention that the buttplate on Model of 1922 #1930 is the second type. I believe the first type was adjustable.
I have forwarded a link to this thread to Lynn Meredith. He is the man that I believe knows most about the International Match Rifles. I don't know if he will choose to join this discussion.
The modified triggerguard/floorplate assembly leads me to think this rifle was made up for international match competition. I believe the Springfield Armory made 1924 IM rifles had heavy barrels.
