Comprehensive Skylab verification test evaluation report (Service Module Reaction Control System), March 1972.  

A comprehensive collection of testing and verification documents in support of Skylab.  Lots of charts, tables, and illustrations (including several fold-out schematics).

This example is particularly nice, as it comes from the collection of Stan Barauskas, CSM Propulsion Test and Checkout engineer for Apollo, ASTP, and Skylab.  Barauskas later went on to work on Shuttle, focusing his efforts on the APU system.  Barauskas authored this report, and it was his personal copy (as indicated by his name on the upper right-hand corner).  

Condition is very good for age.  Slight separation of interior front hinge, easily repaired with a bit of glue.

A great vintage Skylab document straight from the propulsion engineer who authored the report!