FR.. Freno...
makes me think it's italian made..
Sooo Righetti Ridolfi has a very similar master cylinder,
measure the body diameter if it happens to be a 30mm body,
chances are it's the predecessor of the K225 (the one it's reminding me of)
for comparision the K225 outlines:
https://www.righettiridolfi.com/cms-contents/uploads/allegati/SCHEDE_TECNICHE/k225.pdf
You might want to send that picture to righetti ridolfi and ask
(use their contact form on the website and wait for a reply... in order to be able to send a pic)
Otherwise chances are you have a HAASE kart
(also an italian manufacturer)
THEY as far as I know label their brake parts FR##
and with that you do have a righetti ridolfi master cylinder
yeah I'm rather confident tbh...
rebuilt kit... hmmmm try to find a Haase FR11
(that's what I think is easier to find, and since it's labelled FR11... I'm rather certain it's been on a Haase kart)
or go with the K225 rebuilt kit hoping no important dimension has changed.
'sid
[
EDIT]
shoot, yes that is the righetti ridolfi predecessor to the K225..
too bad it's 19mm instead of the 22.2 now...
Means in order to know one must measure the piston ...