You've picked a hard one to crack. The reverse is described as a lis-tipped cross in tressur/Croix fleurdelisée en tressure. Along with the Ecu de France probably the most common known jeton design.
I've played with the image but all I get is SURMATENT, which makes no sense in either Latin or middle French. I put this as late middle ages and the best reference for these types is Feuardent rather than Michiner but it's going to be a long haul.
Something for me to do as the nights draw in. Also with your permission I'll put your images out into the jeton community where somebody may easily recognise the type.
I think the thief will of been just as negged out as the owner when he opened the box , hopefully the owner got his insurance which would perhaps of been more than the true value and more use to the family.
Why on earth they put this on the news weeks later makes me think not much goes on in Plymouth 😉
Genoa ,
Antoniotto Adorno, 7th doge of Genoa (1378).
Grosso
Weight: 3.00 g.
Ex Ercole Gnecchi collection ( sold at Auction Ratto, 21th April 1914, lot 1513).
People say that they get them very occasionally but I believe that not even the entire mintage was released into circulation.
In Zimbabwe in 1964 I think (controversially).