For properties of those hard to find, 100 year old beams, you'd like to save in many historic restoration projects, refer to AISC's Iron and Steel Beams 1873 to 1952. ASIC published this industry staple in 1953. So, its hard to find to say the least. However, this reference provides an historic record of steel and wrought iron beams produced by a dozen or more mills during that time frame. It contains section properties as well as allowable stresses, everything you need to assess the integrity of the insitu steel (or iron).
Also available from AISC nowadays is the Design Guideline No. 15 which contains information on the shapes produced in 1873-1920 timeframe and includes mention of the ASTM process which ultimately changed the industry to produce standard sections. Moreover, this publication provides guidance on rehabilitation and retrofit of old buildings/structural members.
