Don't have one.
When I bought my TT, I recall listening to Steeleye Span's 'Live at Last', and I'd attended other demos with friends and associates, so had already heard the product with a variety of their stuff. I can't recall anything else that I used to audition it.
Last cartridge upgrade, I just bought the cart off the shelf, fitted it, and liked what I heard.
These days, I think I'd find it difficult to force myself to listen to something as a reference disc if I wasn't actually in the mood for it. Perhaps this is why the TT has remained unchanged since the 1990s.
I have a brace of Sheffield Lab and other direct cuts, many of which probably qualify as 'reference' material, but most of them spend their lives vertically, on the shelf, while I listen to other stuff.