Dave (PRRMP54),
Your single bay covered hopper is very similar to one built by Tom Smink (chairman of the 1991 O Scale National in High Point, NC) back in the 1980s. Tom's car had 100 ton trucks and was lettered for Duke's Septic Service and was car number 2. Car number 1 was a shorty tank car. I don't know what happened to those cars and Tom passed away many years ago.