I am looking at a couple of Squarebacks (early 70's), which are in pretty good nick, RWC. The sellers all say there is no rust or just a little small section which has been repaired??

One of them has been recently resprayed (~over 2 years ago), which might make it hard to determine the amount of rust.

What and where should I be looking for hidden rust??

This could open up a can of worms!!!!!

everywhere trust me, each late type 3 I have own had rust in different areas to each other.

Yeah, they rust everywhere. Front inner fenders, spare tyre well, gutters, sills, door pillars, inside the doors, everything and anything. Someone recently posted a warning to look for rust in the cargo floor between the engine hatch and the back seat, which seems a ridiculous place to rust. Mine didn't have it, but the car he posted photos of sure did.

No rust is a lie.
I think they came out stock with rust. Haha.

For me there has not been a common rust point. every car was rusted in a completely different areas.

I have had 70,71,72 and a 73 model.

The 71 purple notch I have now is the first one to be rusted in the re enforcement area in the inner guards.
its the first to have such bad door sill but drivers side is perfect?

The 70 notchback was nothing but rust. there was no floor at all just the heater channels and tunnel. all panels and doors was gone, yet the inner guards where ok with tinny bit of rust.

The 72 fasty was really bad in the front apron and "c" pillar, bit in the doors and tinny bits all over. Was a coast car.

The 73, was 100% perfect in the inner guards, apron and the whole front area. also the sills where 100% perfect as well as the floor. The roof was a different story, rusted out bad.
Also there was no front section of the bonnet, and I mean nothing. Was a single rust hole spanning the whole height and width of the front of the bonnet. About 10kg of bog fixed that