Rob,
That’s a normal C.4596, the second size of the set of four open-enders with JAGUAR stamped on them, introduced with GARRINGTON branding in 1951 for Mark VII and 1954 for XK140.
The T/W branding retained same part number, but this new brand was not introduced until c1958 for XK150, Mark 1, Mark 2 and Mark VIII/IX augmenting supplies of GARRINGTON brand until both superseded in early 1960s by a third then a fourth brand. So can be found c1958 to c1963/4 in sets of four T/W, or mixed sets of four T/W and GARRINGTON brand.
