Brass carriage clock its got 303 stamped all over the inside and i think a little triangle above one of them well thats what it looks like cant find no makers name on it

I was handed it down years ago in a box with a vority of stuff of my nan. It ended up going in the loft. Icleaned the loft out and came across the box and this was in there ive no idea where this clock was made or who made it and would apreciate it if you could give me a small histoy lesson on it