UNIT (crane & shovel corp.) 271-C info wanted

[librarian62]

Looking for spec. sheet(s), sales catalog/brochure(s), ANY pics, and info regarding this machine.
I did purchase a couple of magazine ads (one from 1961, and one from 1968) on ebay. Also obtained a rather vague (reprinted/copied) parts book, with equally vague operating instructions. There are pics of one on the "machinery trader" site. The "albumMMT" Italian site has an image of the 1968 ad. Beyond that, there is nothing.
The uploaded image is of the 1961 introductory ad.
The UNIT 271-C was introduced in 1961, and was produced until @ 1970, or maybe a little later. It's a 1 cubic yard convertible crawler excavator (or 25 ton crane). Also offered as a truck crane (271-T), or wagon crane (271-W). Crane ratings may have been higher for wheel mounted machines.
Some features I know of are: GM 4-71N power unit with either a plate clutch PTO, or an Allison torque converter (no other engine options known to me at this time); oil cooled swing clutches; double ball-bearing swing circle; and a dragline fairlead mounted inside the base of the boom.
NOTE: The 271-C listed for sale on the "machinery trader" website shows what seems to be an over-used "replacement" fairlead of the revolving type mounted on the machinery deck, unlike what is pictured in any other image I have, including the drawings in the parts book I have.