As several have said, check the engine build plate below the starter.
Your YM2000 will probably have the later series engine 2TR20A-X, since that photo shows a second-series hood, about 1976-1979.
Look for red paint under that green. Yanmar never used that shade of green.
For a price comparison see the YM2000's on Ebay. If yours really has only 840 hours and no major repairs then it's at least the equal of the "reconditioned" units sold there for around that price.
Yes it's a 'gray' but this model is extremely well supported with parts. There's a flood of them being imported presently and plenty of parts as well. They are great tractors and I'm sure you will like it.
Your YM2000 will have the same specs as my YM240, the Americanized version of that model. See the photos and brochures referenced in my sig, below.