Good afternoon and thanks for the note Rodm. The Series "O" of the late 20's and early 30's is most like the later 10L's, 13's etc. The one book we have that covers these later models will be useful but is by no means an exact match for your needs. For instance many components of the apron will have identical functions but the design and layout will look different. In the series "O" there was no oil reservoir in the bottom of the apron with wicks to constantly lubricate everything but since the "O" used direct oiling through access ports on the front of the lathe, it accomplished the same thing. Same for the headstock, no capillary oilers there to keep the spindle lubricated continuously, just oil cups that you top off each time before you use it and it gradually ran out over time. If you understand the design and function of the later models it is only a short step to understand the earlier models since many of the alterations SBL did over time were to make the lathe design more robust, more forgiving and less likely to be damaged from improper lubrication. The book does cover the single tumbler gearbox which is the earlier version most like the series "O", and since that is one of the more complex parts of the lathe, this is where you would get the most benefit. You might also do a search here on PM as I believe I've seen a pretty good write-up on the series "O" gearbox around here somewhere. Best Regards, Steve