Correction, no 5 (Blue dial) has a convex case. (I'm going to look into this, it may have been available in concave too)

Stewart

: Tim,
: Probably! It's all very confusing :0)

: 7750 Movement series model no's and description.

: 1) 750.501 Concave lip barrel case, Black PVD, Pasadena. (Earlier
: models had Pasadena on the dial) (In OTD catalogues 1979, 1981
: Speciality, 1982 Speciality)
: 2) 750.503N Concave lip barrel case, circular brush effect S-Steel,
: Montreal. (Earlier models had Montreal on the dial) (In OTD
: catalogues 1982 Speciality)
: 3) 750.503N (yes, same as above but different case) Convex barrel
: case, Starburst S-Steel. Montreal. NO NAME ON DIAL IN ANY
: CATALOGUE, always day/date (OTD catalogue 1977, 1978, 1981
: Speciality)
: 4) 750.501-3 Concave lip barrel case, circular brush effect
: S-Steel, no name on dial, date. Not seen in any Catalogues on
: OTD. This is a strange model, as it clearly has the model
: numbers of a Black Pasadena, but is Stainless Steel, so Heuer
: added '-3' to denote a stainless steel Pasadena. Because of this
: confusion, it is sometimes referred to as a Montreal.
: 5) 750.503B Blue Dialled Montreal. Concave lip barrel case,
: circular brush effect S-Steel.

: Hope that helps.
: Stewart