It's a Mitre Saw - you might have said...
This might help...
http://www.free-instruction-manuals.com/pdf/pa_425321.pdf
There is some doubt in my mind about the number you give 510L - 210 works with more results - it suggest a a 10" diameter cutting blade - 510 mm would be an unfeasible 20" blade!
Good Luck..., July 2016