Twin Cities Ordnance Plant, Minneapolis, MN would have been making ammunition to fill U.S. Military ammo contracts, so I doubt it's 7mm or 8mm stuff.
I note that it's got a black tip on the projectile, so that means that it's AP. My guess is that it's .30-06 for the Korean War era belt-fed of the day. It'll work in a BAR and Garrand too.
I've cleaned corroded ammo like that up in my tumbler before. No it doesn't harm anything and no it won't set-off the ammo in any way. Steel wool will be required for some of the stubborn stuff, but the truth is even dirty ammo like that will fire just fine. It's just not pretty & shiny to look at.
also would be good to pull out the calipers to measure and make sure.
I've heard of people using ammonia for cleaning solution in their tumbler but for certain would not recommend that. But a rag or steel wool with a small amount to wipe and then clean off should be OK I would think? I guess just avoid it to be safe.
Even just a good once over with a rag or fine steel wool should be plenty to remove most of it, enough to inspect and fire.
Twin cities 30/06 AP --
I cant read the number clearly but if 1950 it is corossive primed --
1953 is marginal --may or may not be -- I forget exact change over date.
The brass only needs to cleaned well enough to chamber -- But it should be checked for big pits --
My advise to to use caution if tumbling it. The danger isn't really it going off, but that the powder granules might be sufficiently rubbed together and create a fine powder layer, as well as rub off any retardant, depending on the powder used.
This could create a faster initial burn and a spike in pressure.
Just a caution.
I have some that look like that from a belt for a 30 cal. machine gun that I have from Viet Nam. The only difference there was an orange tip tracer in the belt. We used to shoot them in our 30/06. I still have some, somewhere in some 30 cal ammo cans.