Doesn't Mike Acres site have anything?...let me open a new window and look.
Ah, back again, and it looks like Mike Acres site is experiencing technical difficulties.
here's what I think Iknow: the 605/610 were basically the same saw, but I believe the 605 was about 57cc, the 610 about 60 or 61 cc. Both were available from about 1975 or so, also available in Monkey Wards versions at that time; indeed the very first one I ever saw was a brand-new MW saw on a homemade sawmill rig...was not impressed...this was about 1974-75.
You could get one equipped with up to about 24' bar (I have one like this w/ .354 McC chain) but I believe they were more commonly seen with 16" and 20" bars.
After about 1980, they made some of these (actually a lot) disguised as the Timberbear, and I think they might have been available in both larger and smaller displacement sizes. These were sold mostly in big-box stores, and I think you could still find new ones (collecting dust, mostly) for sale up until the mid -'90's. I don't think any were actually manufactured for sale after about 1990, and I thing the plain yellow ones dissappeared from the assembly lines long before that.
I have had some bad things to say about them, but within their niche, I suppose they were an acceptable unit. Not a lot of power, kinda hard on fuel, loud, anti-vibe isn't real good, and heavy. But they do cut wood once you get past that. My biiggest complaint would be that they are ugly, actually.