UPDATE Spring 2023. Ironically, Art Thief is missing. The box containing the stamp cannot be found among the bookshelves in the living room. Bookshelves have since been erected in the main hall between the coat check and gift shop, so we attempted to look here, in case someone moved it with books. Alas, the massive museum signage, hung in front of the hall bookshelves, obstruct one from searching effectively. The books appear to function as mere decoration.
As luck would have it, Anthony Amore, Director of Security, investigating the infamous Gardner art theft, happened to be on site when we discovered this additional missing piece of (letterboxing) art. He was sympathetic to our cause, but had no clues to solve our mystery.
If you find the box, please let me know! For now, I’ll mark it missing.
Is the letterbox hiding behind the giant museum signage blocking the bookshelves?
Would the staff allow me to search the shelves more thoroughly?
Has the letterbox been stolen yet again?
Who stole the other works of art?
We may never know the answer to this, or many other mysteries of the universe.

This letterbox will be recarved and replanted again one day.
Do check back.

A gem!

Thanks for the previous comments. The coat room is still accessible and the box behind the staff. Very helpful staff and awesome stamp. Paintings still missing but HH available.

Wonderful

We've wanted this one for quite some time......thank you!

Gorgeous!!! Because of covid, the living room currently serves as the coat/ item check, but the attendant was super helpful and excited to help ;) it took us a couple minutes, but we successfully found it. Thanks for such a great carve!

Great carve and location! Thank you!

We loved this find! Very well done stamp and tricky spot! We were very careful to stamp and return it on the sly.

Traveled to Boston to celebrate my 30th birthday and this is one of the stamps I found while there. Very neat carve that fits in well with the history of the museum (which has tons of other great art to appreciate). A bit hard to be incognito when getting this stamp, but I think it all went well.

Wow you really have to be careful here so no one sees you. Great stamp. No one seemed to be watching us so I think we got away scott-free.