My how quickly we forget The Daring, Thomas Carlton and the Mikula all had reversible Fairbanks and I believe the Bartlett and Provo Wallace were fitted with reversible 4 stroke Merlees.
Deutz also makes a 4 stroke reversible engine with separate valve block assembly on both the engine driven lube oil pump and on the Fuel Oil Booster pump
Just about every engine built before the advent of electronic controls and electronically controlled injection, even the engines with electric pumps, has at least one reversible oil pump everyone seems to forget about namely the oil pump in the Governor eg. Woodward PG & UG8 Governors. There is a simple drawing in the governor book that shows the check valves and would be easy to reproduce and explain in an exam. Mechanical Governors with an internal hydraulic system such as the Woodward PG & UG8 can be used in any number of configurations and must be able to work in both directions of rotation.
- Woodward Governor Oil Pump
Troubleshooting 101 "Don't over think it - K.I.S.S. it"