There is also that pesky airworthiness directive from 1974 that requires the lavatory ashtray as well...
(c) Except as provided by paragraph (d) of this AD: Within 180 days after August 6, 1974, or before the accumulation of any time in service on a new production aircraft, whichever occurs later, except that new production aircraft may be flown in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to a base where compliance may be accomplished, install a self-contained, removable ashtray on or near the entry side of each lavatory door. One ashtray may serve more than one lavatory door if the ashtray can be seen readily from the cabin side of each lavatory door served.
(d) The airplane may be operated for a period of 10 days with a lavatory door ashtray missing, provided that no more than one such ashtray is missing. For airplanes on which only one lavatory door ashtray is installed, the airplane may be operated for a period of 3 days if the lavatory door ashtray is missing.
NOTE 2: This AD permits a lavatory door ashtray to be missing, although the FAA-approved Master Minimum Equipment List (MMEL) may not allow such provision. In any case, the provisions of this AD prevail.
74-08-09 R2 - Transport Category Airplanes