Thank you for the info. I greatly appreciate your posts. Some things jump out from the pictures. Firstly the location of the oil window on the headstock and the lack of vin tag on the head. It's on the tail. I'll dive in more when it arrives back in TX.
I think there is room on headstock for data tag, as 13"s from the 1950's had it there. The site glass location I would think because its a different casting then the 16". The 13" headstock, tailstock, are definitely smaller in size than a 16", maybe carriage and apron too.
Just about a year ago I saw two 13's at an auction in Houston. If you click "see item details", you can still go through all the pics. A regular 13":
Lot 116 at Machine Tools and Surplus Assets to a Major Oilfield Research & Development Center from Harris Auctions.
www.bidspotter.com
And a plus swing 13", with 20.5" actual:
Lot 118 at Machine Tools and Surplus Assets to a Major Oilfield Research & Development Center from Harris Auctions.
www.bidspotter.com
When I saw them first hand, I could see physical size of headstock was smaller than my 16". Some pics from those links:
If you do call Monarch for the build sheet, get the service and parts manual too. It comes in a nice binder. And you'll notice in the parts section, many 13" parts are on a separate page from identical 16" parts, due to size making them a different part. In fact, I would gather the smaller size is what allows the higher top speed on headstock.