ULA has previously suggested that a future version of the Vulcan rocket may reuse the engine section by separating it from the first stage and recovering it on the ground. They call this "SMART reuse".

In 2023, Tory Bruno, the CEO of ULA, said

> In terms of our engine recovery, that is going to happen within a handful of years. I don't want to say exactly when because it's part of the contract we have with one of our customers at this time, and we're not releasing the details of that. But it will take a couple of years to actually be reusing the engine.

Source: https://arstechnica.com/science/2023/02/after-vulcan-comes-online-ula-plans-to-dramatically-increase-launch-cadence/

This market will resolve YES iff they launch a rocket that uses at least one engine that has previously been fired in flight to achieve earth orbit by the end of 2030. This includes but is not limited to SMART reuse. E.g. SpaceX-style stage recovery would also qualify.