Cripes a lot different boat to the shoal draft wing keeled Catalina 27 which has the hull design circa 1970. There was a standard keel, deeper keel, shoal draft winged keel and two different rig sizes. Build quality as mentioned in many reviews on line is probably not as good as the NS30.
The NS30 is the Peterson Santana 30 1/2 ton circa 1975 IOR design, with step added to transom - see here; but I see your boat has the original transom with a ladder - so still easy to board. If it is called "Santana" as evidenced maybe it is a Santana 30.............but the condition looks like a 1990 build so could be NS built before they changed the transom to include the step. Check with the dealer whoever that is - normally dealers will advise their name.
www.google.com/search?q=north+shore+30&rlz=1C1GGGE_enAU475AU522&oq=north+shore+30&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIHCAEQABiABDIHCAIQABiABDIHCAMQABiABDIICAQQABgWGB4yCggFEAAYDxgWGB4yCAgGEAAYFhgeMggIBxAAGBYYHjIICAgQABgWGB4yCggJEAAYChgWGB7SAQ41NDAxMzE3MzBqMGoxNagCALACAA&sourceid=chrome&ie=UTF-8#fpstate=ive&vld=cid:23430068,vid:SEk6sZ11dCoThe NS30 is a far better boat and I would simply go and buy it pronto, forget the C27. Good diesel (Kubota based) and seems well kept. 4 sails. How old is standing rigging? Expect need to survey it for comprehensive insurance.
You've probably seen this link - seems like around 1978 design not 1975.
www.seabreeze.com.au/forums/Sailing/General/Santana-30s--Peterson-30s-?page=2