Thanks for taking the time to post the extra images , kluksu !
It's sure tough to give a correct id on this one (for me) .
The realest & most accurate advice from me to you is :
1. Loosen those strings until they have no tension in them .
2. Don't clean it !
3. Get thee to a very good luthier , or a violin 'pro' for an correct I.D. on this little guy .
I'll just ramble on a bit about your fiddle for a min. , though .....
It is known that the Gabrielle (aka Gabrielli) 'shop' in Florence produced good quality violins & that they used a yellow varnish & written labels ( & did so in the 1760's) .
Yours seems to show lots of dings & small dents & possibly some 'worm holes' too (?) ...such marks can be a sign of both antique instruments & copies , as well as those intended to deceive (fakes) .
The very dark 'dot' on the back (where it looks like there's been a repair) near the base of it's neck is possibly iron corrosion from a steel/iron nail .... you might want to get a magnet & see if it holds onto it .
If that is a nail , it's a repair not done by a luthier !
Sometimes various violins were 'repaired/reassembled' in a manner which marries parts from other , non-original parts ... including major components of necks , fronts & backs .
I've seen a few hundred violins in Europe , many of which were survivors of wars over there & were repaired 'roughly' enough for them to be played again (times were extra-very tough after WW2) , esp during reconstruction periods .
Some of these old boys can play real sweet , too .
Maybe you've got a real pearl there , even if it does need work , kluksu !
Still being a pest , maybe could you post a pic of the side , front & back that do show the complete & entire instrument ?
Also ... where did you find this cool little item ?