I believe they were wooden flat-bottom gondola cars . . . about ready to bust in the middle.  Good catch. 

 

The C&O kept 40-ton wooden FB gons and hopper cars around through WW One to meet demand for more cars . . . . didn't interchange them and mainly used them on short runs from mines to say blast furnaces.  They had a set of 30-ton wooden gons that got 40-ton trucks and were used to carry limestone on daily twenty-mile round trips. Pig-iron operations picked older cars also. to shuttle materials between various operations on branch lines into the twenties.

 

Al Kresse

From: "'Schuyler Larrabee' schuyler.larrabee@... [STMFC]"
To: STMFC@...
Sent: Sunday, June 7, 2015 11:26:22 PM
Subject: [STMFC] Hoppers from early 20th century