As you noted, these are older chips (jetons) from the Monte-Carlo casino in Monaco.
Your jeton is probably cataloged in the Thomas Day catalog, listed in denomination order.
You can see a pdf copy of this catalog at:
http://cctn.ccgtcc.com/montecarlo.pdf
Unfortunately, it's in black & white, and doesn't have specific dates.

Check to see if your jetons have a "funny" smell to them -- sort of like vinegar or formaldehyde.
If so, they were made of a early form of plastic (around 1920's + or -) that gives off these gases.
Over time, these can become brittle and/or warp; the colors can darken or change with age too.

They are interesting objects, but generally not all that rare, even though 80+ years old.
Lots of them survived and are found as collectibles.

A nice memento of you mom, nonetheless.