When I was an undergraduate mail to "tzs, 1-59, 91126" would have probably got to me.
91126 was the zip code for Caltech undergraduate housing, which would have been sufficient to get the letter to the Caltech post office. The Caltech post office would have recognized 1-59 as the building code for Ricketts House and put it in the bundle of mail for Ricketts. The carrier there would have put it in the "T" box in the mailbox array in Ricketts lounge.
91126 was the zip code for Caltech undergraduate housing, which would have been sufficient to get the letter to the Caltech post office. The Caltech post office would have recognized 1-59 as the building code for Ricketts House and put it in the bundle of mail for Ricketts. The carrier there would have put it in the "T" box in the mailbox array in Ricketts lounge.