Re: I ain't no expert, but.......

Taylor, the story about the the Mike's being number 101, 102 for use by OLC is open to question. Jim G. and I were talking about it yesterday, unaware of your update. 2 things that make this questionable are that OLC already had engines numbered 101 and 102 which were Shays. Also the 19 and 20 with their large drivers, large cyl. size in relation to weight on drivers with 170lb. boiler pressure made them more suitable as high speed (for NG) pass. engines, than for slow speed freight operation on a logging line. I found a reference on the internet a while back to proposed construction down the middle fork and a connection to someplace. I know this was an alternate route in the proposed construction of the SVRy to S.Central Ore. and a connection with the NCO. pre 1912,but I think the thing I was reading was much later, as in the early 20's when the middle fork line was built. If I get a chance I will try to find what I was looking at as it was new history to me. It may be that 19 and 20 were envisioned to operate on the water level grade to someplace beyond the John Day Vly. that was never built to. This including what you have included may be too much supposition as far as why they were numbered 101 an 102 to be on their roster info.
Also Taylor, I would not include the bit about 19 and 20 used in helper service unless you have some real good supporting info on that. At least in the summer of 1925, it appears that 19 and 20 handled trains out of Austin pretty much the same as the Baldwin Mike's. It appears at that time, whatever engine happened to be available at the nearest location to the summits was used as a helper. I don't see a particular trend. Perhaps we can look at some conductor reports together this Spring to see what operational practices seem common. I will say that in the later days of pass. service on the line there are a number of photo's with both 19 and 20 as the pass. engine with a mighty consist of one car.
Also regarding oil burning, there are various photos of 19 on the SVRy without a spark arrestor stack, but burning wood. From the info I've seen, 17 was the only Mikado converted to oil by the SVRy.