I saw this in an attic in a 1958 bungalow. It looks like a tin barrel with a vent or fill tub that extends to the underside of the roof deck. The roof is obviously not the original roof and there was no visible penetration on the exterior surface. I am sure it has been decommissioned but I have no idea what/why it was originally installed in the home. (as it would definitely not fit on the hatch) You will note it is insulated and it has a bearing wall below it. I was thinking it may have been a rudimentary solar exchanger but see no evidence of anything unusual in the utility room. Any help would be appreciated!