6G Thirty

Hello ACMOC,
I have been asked to evaluate a 6G Thirty tractor, but it's hard to find much information. The Chrisco list doesn't show anything, I found some old threads enough to tell me it was a transition between the Thirty and the R4, only about 800 built?
It has sat for a long time, engine is stuck, exhaust uncovered, carb gone, mag is there. Manifold is pretty much rotted out. Sprockets & rails pretty good. Not pristine but runnable...grousers have been built up with ice bars.
There is a belt pulley attachment, but the pulley itself is shot...
So is this thing rare & desirable? Orphan? Any way to find the exact year? SN is 6G5XXSP.

6G495 to 6G787 is 1937 and is listed as a "Thirty"
6G788 to 6G930 1938 is listed as "Thirty/R4"
6G931 (1939) - up is "R4"

Thanks OM.

I may be all wet on this information, but I was told that most of the drive train is the same as the RD4 and some engine parts are interchangable. A friend near me has a 6G 30 and knows a lot about them. I believe it has far more in common with the RD4 than it does the earlier 30s. If you want a rare Cat , it fits that category very well. Good Luck, Grant.

I didn't need it, so I told a friend that did need it, and was able to rescue it...