The easiest way to date a Holdsworth, Claud or Grubb is to start with the frame number. This can give a very good indication of when the frameset was made and sometimes much more. Knowing the year made narrows the field enormously when trying to ID the model. Pre 1957 Claud Butlers can easily be dated to the exact month from the frame number alone. Most pre-war Holdsworth's have the frame number on the seatlug. Post WW2 it is generally under the BB, but some 1950's models are stamped on the rear dropout, drive or non-drive side.

Unfortunately the number is usually coated with enamel. On some frames, where the paint is thin and the digits well stamped the frame number will be easily read. If the enamel is thick however, it often causes a digit mis-read, especially when digits are badly stamped. On rare occasions. a digit can be completely filled with enamel and rendered invisible. Fortunately, the same frame number is also stamped on the fork steerer tube, irrespective of year made. The number is much easier to read here, because it is not painted over and protected inside the head-tube, every digit will be clear. Pre 1957 Clauds may also have a builder code stamped with the steerer tube number, this is not stamped on the frame.

To date or ID your model you should ideally remove the forks and take a clear pic of all steerer tube numbers, also get a pic of the frame number from the frame if you can. Matching numbers should confirm each digit of the frame number and that the forks are original to that frame. They usually are, but this is useful because then the fork crown, lamp boss braze-on (or lack of one), dropouts etc may be used with confidence as model ID features. Post the pic(s), clearly showing the frameset serial number, to a web-based discussion forum (see classic links on home page). Some of the enthusiasts should be able to date it for you. If you want to ID the model, also post close-up pics of key ID features, like headlugs, seatlug, fork crown, dropouts, decals if in original finish, headbadge etc.

A database of frame numbers found on the internet can be found on this link. This also includes charts of potential number progressions for each numbering style used by Holdsworth, CB & Grubb summarised below.