It use to be that you could order sewing and craft patterns from companies that would advertise in the local newspaper. This one is a Marian Martin printed pattern 9139. We know that it's from 1971 from the postmark on the front of the envelope. The pattern is for a sleeveless dress.
This pattern will fit a misses' size 14.
Bust: 36 inches
Waist: 27 inches
Hips: 38 inches
Finished back length from neck to waist: 16 1/2 inches.
The pattern is cut and we made sure that all the pieces were accounted for - 10 pieces in all. The envelope is in decent condition, it had been opened on the bottom, probably with a letter opener. The paper instruction sheet, which is shown in the first photo, is slightly yellowed with age, however it is still very readable/usable. The tissue paper sewing pattern has been gently used and is in very good vintage condition.