The Museum Press was an offshoot of the Charles Hamilton Museum and reprinted some of the rarer Hamilton stories. You can find more information on the Museum Press in the publications section of  The Greyfriars Index

The Museum Press published the book The Charles Hamilton Museum Illustrated for the London branch of the Old Boys Book Club.

The Fatal Box - a Ferrers Locke tale by Owen Conquest.

This story was originally published in Magnet 809 as "The Third Brother".
It was reprinted in The Popular Book of Boys Stories in 1923 as "The Fatal Box"
before being reprinted yet again by the Museum Press.

Charles Hamilton Calendar

The Museum Press published a Charles Hamilton calendar for 1982. It was illustrated by Chapman the main illustrator of the Magnet but unfortunately didn't contain much material that could be considered relevant to Greyfriars. Thanks to Naveed you can find a scan of the calendar here.