Arrr! It's a 19 inch then. I sold a 19 because I found it too big, but I let it go before I could find a 17 to replace it with. Oh well, good luck and lovely bike.
Hmm I would have said that it was a 17.5" as Marin used to measure their frames center to center and therefore a 19" would measure more like 20.5" to the top. But since they stopped using inches and went small, medium large etc its hard to say. Its too small for me unfortunately as my bikes measure around 20" to the top of the seat tube. I would say this would suit someone 5ft 10" to 6ft 1"?