First post here, hopefully can get some help. Working on a house built in 1965 and has virtually been untouched. There are about 5 coats of paint on all the returns and they no longer function appropriately. Impossible to close or open most of them. Trying to find some cheap replacements but haven't been able to. The internal dimensions are 11.5" by 5.5" and 11.5" by 6.5". Was also thinking about sandblasting them, but didn't know if it was worth it at this point and if that would actually return all the functionality at an affordable cost. Any help would be appreciated!! Thanks!