I have a P-25D and a P-25C, Adam. They are earlier versions of the P-25F. The C was made 1978-79, the D 1980-83. When my brother was here about a month ago, I gave him the P-25D to use, and we played together quite a bit, with me using a 1970s Suzuki A-25. It’s almost identical in sound and functionality to the P-25F, though the P-25 has been refined in successive models, and I would choose an F over a D, and a D over a C. My P-25C has a bit of the sticky keys issue, but the P-25D does not.
The big jump was from the P-25B to the P-25C.
The photo in the Reviews page for the P-25F is actually of a P-25D.
The distinguishing features of the P-25D are two-tone coloring (cream on the bottom), the “Pianica” label, and “Made in Japan.” I paid $45 U.S. plus $15 for shipping, which is about the same as what a P-25F costs. I think the P-25D is worth that, but I also believe you could, with patience, score one for about half that. These models are pretty durable. So if it looks good in photos, it’s a relatively safe buy. These are very nice Pianicas.