I have no pictures of Y-66, the list of 044's don't give any numbers of Franklin/Sproat yarders. BTC, is the yarder you are falling for a high rise cab? Is it a dbl main (easy to see, it have 2 big fairleads close to top of tower in addition to the haulback fairlead on top). I have pictures of 2 dbl mains from Franklin, Y-55 and one unknown. In addition I have picture of Y-50 which is a tag and at least 1 more unknown tag. From Sproat I have pictures of 2 dbl mains, Y-18, which I made hours of video of, and Y-02. Y-01 was a Cypress 7280, loader here was L124, a Cat 235. I have also videos and pic's of a spar, the former Kelsey Bay yarder J-20 (Skagit BU-98 sp). It was operating with a hydraulic loader L 38. By the way MMB had 30 -thirthy- 044's.
When first getting into numbers I have been able to decode some others: I have pic's of 3 046's taken in Franklin somewhere: J17paired with L26 (Cypress 7230 with boom), J133 (the one from the pic's eith carrier/yarder standing parallell to tower) paired with L161 (Cypress/American with boom) and J21 with a Madill 075 snorkel. That was the 3 046's operating in Franklin, the newest (I would guess J21) was purchased by MMB Cameron, the other 2 Franklin. MMB only had 4 046's but one burnt up.
Jackd, the list is in the dropbox, it's an Excel spread sheet, have been there all along. BTC - hope you can take some pic's of Y-66, or at least try getting the serial. It's on a plate under the cab or it also may be on the maintenance chart on the cab door inside.