thanks gwr - I was trying to see if it is possible to date Parkinson's vices but I suspect it will be very hard to tie down to a very narrow date range. Here is what I found out:
We know the Parkinson
perfect instantaneous grip was made from 1895 onwards, the earliest picture I can find of the woodworkers' model is from the Charles Nurse 1891 catalogue*, and it shows a design I have not seen elsewhere:
... possibly this is the very first model?
After the model with a front jaw like yours is introduced there are some variations (some have a long rear carriage, some short; some have three holes to mount a wood insert to the front jaw others two) but I haven't been able to find any evidence that would match dates to the features.
The only aspect I am reasonably confident about is that at some point Parkinson's moved the spring from under the half nut to behind the front jaw/next to the lever.
I am not sure why having the spring near the trigger is a better solution, but it was clearly the later development and the one that caught on in all subsequent QR vices of this type. I can't find out exactly when this changed occurred, but I believe it happened after Record started manufacturing their QR vice (1917/18 earliest) because Record made both kinds early on. This is based on an assumption that if Parkinson had already discovered that changing the location of the spring was a better design then Record would have copied them immediately when they launched their version. It is also possible, of course, that Record were the originators of the change rather than Parkinson.
I did manage to find a late-ish catalogue entry with both the Parky that looks like yours (including 3 screw holes in the face) and the Record model that would eventually render it obsolete:
https://archive.org/details/illustrated ... us+grip%29
archive.org has this catalogue dated as 1910, but there is no date on the catalogue and I do not think it can really have been produced before 1927, which is when Miller Falls introduced their electric drills (see p. 80 where they are listed)
As you can see, Record undercut the price of the Parkinson vice and, since theirs' was clearly a superior design, my guess is that they would have quickly eroded Parky's sales. Indeed, by 1930 pretty much all UK QR vice production had switched to using a Record-like design (even Parkinson had a 'perfect' version) and by 1935, at least according to the Buck & Hickman's catalogue, the old Parky pattern was no longer available.
so after all that, we can conclude (what you had probably known anyway
), that your vice was most likely made in the 1920s.
*available, with other catalogues, from taths.org if you sign up as a paying member.
Buck & Hickman 1930:
If I had to guess then I would say this is the final version of the 'Parky pattern' (including two screws and short rear carriage).
B&H 1935: