Do You Recognize These Housing Plates?

We need your help understanding these plates from the Paraiso Housing Office. What was their function? What do S/R, M/R, and M/T stand for? Were the holes used to hold keys? Would something be written in the white spaces?

1F2F8331-812E-4229-9D47-E49BF0BC5766Front of Plate 1. The back is blank.

BE0E1A7D-277D-47B4-A339-CC1BF6CAB2E8Front of Plate 2.

87E26D14-2889-4CD9-B6D5-D91559454C88Back of Plate 2.