I have a toilet where the tank seal is leaking. problem is i can't find brand of toilet anywhere on it. House built in 1972 and toilet is probably original. Tank is ceramic with "pat 191-697" engraved on underside of tank cover. the refill bowl tube in tank is "built" into the wall of the tank and is ceramic also. Seal, from looking inside tank appears to be about 3-4 inches, although I have not measured it...thanks