From what i understand, the reason they didn’t get any of the German panzer left in the country after WW2 (except a few for de-mineing operations), was because during the Yalta Conference, it was agreed on that German war material should be destroyed. It was the same reason that Denmark used the Spítfires instead of the Fw190’s that were in the country at the time of the German surrender.
France didn’t have its tank industry going at that time, and Britain were in massive dept because the war.
Denmark have never really had their own armoured vehicle industry, the most they produced were a couple of armoured cars.
The reason they did get arms support, was because the Marshall plan, which were enacted in 1948.
From what i understand, the M1A1C, is similar to the M1 on other Sherman tanks, but without the muzzle break.