Welcome!
I think what you have there is a standard RS-series tiller but the version that mounted semi-permanently to a custom mount found only on Yanmars. Then someone cut off the custom front extension and welded on standard 3-point 'ears' to convert it to a universal 3-point implement. That's not a problem, just a 'feature'
- beyond perhaps needing a custom length driveshaft.
Yanmar at the same time also made a lot of RS tillers with standard 3-point configuration, RS1300 is 1300mm wide and RS1400 is 1400mm wide. These were sold up through the late 70's (?) then they went to red paint and '1401' etc to distinguish the next series.
My guess is your RS135 is 1350mm wide. Aside from the welded on mounts it looks identical to my RS1400, see my sig photo below. I'm pretty sure yours shares parts with the 3-point RS versions.
As for tines, the Yanmar tines are more slender than an American tiller, they have more of a slicing action that was probably to cut up rice roots, since the original application was to till rice paddies. But they work fine for an American vegetable garden or small farm. I don't think a few tines missing makes much difference at the slow forward speed used for tilling. Hoye dot com has tines if you need them.
I use my RS1400 on the little 18hp YM186D to get into the edges and corners where the 8 ft disc behind a 50hp tractor won't fit. But this 1400mm size came original as mated to YM2000 which has 20 pto hp, 24 engine, to give you an idea of what you need assuming yours is 1350mm.
These tillers always have water in the bottom of the gearcase due to 40 years of condensation. (Plus a first application of running half submerged in a rice paddy). It is recommended to drain and refill the gearcase a couple of times to get the water out. Normal 80~90 wt gear oil. And the bearing over on the non-driven end of the tine shaft is often found to be rusty. If it seizes it will tear up the mounting area. So dis-assemble that side and repack with wheel bearing grease, or better, marine water resistant grease. It's a standard bearing if you need to replace it.
One last point: I see your rear 'training wheels' (depth control) are mounted with the part that extends down to the axle, like half a bicycle fork, on the inner side of each wheel. I learned I had to swap wheels to put that half-fork on the outside before the wheels would track properly through a curve. That's counter-intuitive because they are more likely to gouge my orchard trees that way - but that is the configuration shown on the decal on my tiller. And I do like the wheels for depth control, because my smaller tractor can be stalled if the tiller goes too deep.
That's about all there is to these. They are indestructible so long as you keep an eye on that offside bearing.
Enjoy!
