If the final check was actually paid in 2024, a 2024 W-2 is appropriate. If you are the person who is entitled to his estate and property, this is considered "income in respect of a decedent." You just report it on your own tax return. If he had a will that required splitting his estate with multiple heirs, you may need to open an estate, get an EIN, and file a tax return for the estate before splitting the rest with the heirs.
https://www.irs.gov/publications/p559
