All right - I remembered to go measure my extra saddle last night.
It is an older, brown leather Passier - Hanover close contact/jump saddle. From the "button" to the middle of the back of the cantel it measures 18"
I am not sure how wide it is - juding from the horses I have used it on in the past, I am going to guess it is a medium-wide tree. I know that the Stubben my gelding uses is 32cm (medium-wide) so I put the Passier in my truck so I can try it on my gelding tonight and see how it fits him. I thought that would give me the best idea of tree size - unless someone knows how to measure for that?

Like I said, it is an older saddle, but is still in good condition. A little banged up maybe, but structurally sound (leathers good, no stitching, etc. coming undone) I am getting my new camera tomorrow and can take pictures if Samantha or anyone else is possibly interested. I ride dressage, this saddle is going to waste just sitting around my house!