I've been looking for a Contessa for years and have poked my head through a large number of them that are for sale up here on the great lakes. I have found none that look as clean and well kept as that one - particularly for the listed price of $19,500usd. If the boat is in as good condition as it looks, then it's definitely worth making an offer. This is by far better than the 1972 one that you were also considering.
Some points that I learned in my search...
Contessa hulls are solid fiberglass, but their decks were cored - and cored with various materials. In every case, I have found rot or moist decks that were about to rot, so be sure that you do a thorough (and not just a spot check) of moisture in the deck.
Spider cracks were also common, some superficial but mostly deep; I've only found one Contessa that did not have spider cracks and my response was to put in an offer (sale pending my surveyors' findings).
Make sure the rudder is hung with 3 pintles/gudgeons. I can't remember if this was a factory option, but many of this generation had it. I read that this is a common point of failure.
Previous Contessa's at which I looked also had various problems with clamps and through hulls; Particularly anti-siphon valves.
Lastly, since there wasn't shore power included from the factory, I've seen all kinds of crazy AC setups. This boat looks to have no AC at all, so you may be ok there.
Some things about this particular boat... and very few things I could point out are flawed.
The stove is in an awkward position, unless you like to cook while on the head. The privacy door has been removed so that the stove could be mounted there so that's a little awkward if you aren't extremely close with your travel mate.
Many Contessa's of this generation fitted an after market traveller as the factory doesn't include it. My observation is that the skippers preferred the traveller, but the traveller often caused stress cracks from poor mounting or placement. This is a personal preference but something to consider.
The Yanmar is a terrific bonus feature. The old Farymann is solid and they still make parts for it, but in my world the Yanmar is more common and therefore there is more assistance available.
If it all checks out, you've found a gem.
If a Contessa is right for you, then snap this up as it won't be on the market for long.
hmph. I broke my "no posting until I've officially bought a boat" rule.
ps If my boat deal falls through, I'll seriously look at this one in Maine! ;-) I've given you notice.