They are smoke grenade launchers. You fired them from inside the tank with the hatch closed because they fired white phosphorous. We fired them during one gunnery and the safety precautions were strict. The M60A1 did not have internal smoke making ability. Maybe the A3 did, but not the A1's we had in 1979. The large things on the sides of the Sheridan turret were also smoke grenade launchers, but of another kind. If we could fire red phosphorous I never heard of it. They were pretty effective in low wind conditions, then you had to get out and reload them, so in combat they had a limited usefulness.
Your right it does look a little like a hoffman device,you'll find on M60a3's the Hoffman was actually bolted onto the main gun tube.what your looking at is the grenade launchers,theres a switch in the turret (loaders area) to set them off, M-1s have them also.Little redundant since M60's had smoke generators on the engine anyways.
Dave the tank had a 105mm main gun tube. The 152mm storage tube was from the howitzer I belive, it was just straped to the tank and it held all the maps for all the area both side of the border it kept all the maps nice and dry.
The ammo tubes were 155mm howitser rounds. We always scrounged as many as we could get away. Sometimes they were difficult to get because they were reuseable and were supposed to be returned to the ammo supply point after shooting. When we traded in the M551s for M60's we of course kept all the storage goodies we had. The multislotted tubes are for smoke generation. I'm pretty sure they fired red phosphorus, maybe white phosporus lke the Sheridan.