Adrian, It all depends if you just want a toolbox, or the right one for the year. Like all businesses, survival is the aim, and BSA would use up what they had from previous model years so there is evidence that rigid style triangular toolboxes were used on the early plunger frames. Once introduced, the larger basic plunger toolbox profile then remained the same, but I have come across boxes with an essentially flat lid, as on early S/A models, and the more widely found slightly domed lid with less angular edge. This could account for the differing part numbers.
65 9080...A7/A10 Rigid Type, Fitted up to 1953, so can be found on Plunger Frames. Triangular profile to fit snugly into rigid chainstay aperture. Leaves a gap underneath when fitted to a plunger frame.
67 9007... A7/Star Twin, Spring (Plunger) Frame fitted until 1951.
67 9002...A7/A10 all models, 1951 onwards. Larger toolbox to fit completely into the plunger chainstay profile.
An original Plunger Toolbox will have a horizontal metal strip just above the lower edge, parallel to the hinge, to stop the tool roll falling out when vibration opens the lid at that inconvenient moment. As far as I know this is absent on a S/A toolbox, but I could be wrong. This may help identify what toolbox you have. Plunger toolbox also has two bolt holes to attach to the mudguard, plus a locating hole for the frame tube clip. S/A toolbox has completely different mountings, so look for evidence of their removal. Even so, the S/A Toolbox would be awkward to adapt, and the fitting of one is unlikely.
There are two holes to mount the toolbox on an original rear hinged type mudguard, bottom hole just above the lower frame chainstay.
Roy Bacon's Twin restoration book shows the confusion. Page 13 shows a 1951 A10 Plunger with a triangular rigid frame type toolbox, and a 1950 A10 which appears to have the larger, more common toolbox, with the rounded top profile.
The eBay one would do, looks OK even down to the tool roll strip, but like all parts sourced this way, quality may be an issue. If you decide on this product, choose a UK based seller. I don't like the uncertainty of hidden import costs.
Swarfy.
