D series 965968 is from the early Big R period. I am curious, are the knobs on the strainer and throw off solid top or rivet top. And the Drum is COB.

Ploughman, not sure if I understand the question 100%, so here are some pics. And, I think you and Dan are correct, it is brass. I tried the magnet test with a cheep ref. magnet. It did stick ever so slightly but is that due to the chrome plating? The magnet had much more resistance to the hoop.

Got the drum from Don Bennett drum studio.

Your knobs are rivet top. The change happened with drums very close to your serial range in the early XP8 period.