Beautiful collection.
I'm still learning, but this one of mine is from 1931. Rick has some great data on the 99H's, wish I could find his old post on it. I was thinking the carbine buttplates showed up for a few years in the middle of the barrel band run, but early and later ones were shotgun style.
Edit: Couple of notes I have from Rick on shotgun buttplates and barrel bands:
1) Not everything you read in Murray is correct. This is why I did the disply on the 99-H. There are three styles with at lease eight variations. The first barrel bands up to around 340xxx had shotgun plates.
2) Yes, 1931. The style was changed that year to add the band and the pads. THe second picture in Murrary is from the 1931 catalog and I think it was an early Savage drawing of what they thiought they would be producing. I have not found one like pictured and I do not think they were produced.