TV surface swival security mounts

Question

My husband and I own a small motel, we bought some used tv cabinets that already had tvs in them. These tvs are 10 + years old so we want to put our tvs in the cabinets because they are newer and bigger. The problem is the tvs in the cabinet are on a sviwal mount and we can not figure out how to get them off the mount. These are probalby old moldels judging by the age of the tv. Please help before my husband ripps the cabinet apart!!