Does anyone recognize this RPO postmark? I believe it is dated March 30, 1934 (TR24) and it would seem "Woods Hole & Bos. R.P.O" as the most likely marking:

However, when I tried looking up the RPO postmark, all I could find were postmarks printed Bos. & Woods Hole, as in this example:

Could it be that there were two different devices used on that line depending on the direction the train was heading?