The other day I broke my own rule of not buying any more of those turn of the century imported student-quality sets sold in vast quantities, primarily by Jackson Brothers, but also by AG Thornton and many others. My impulse purchase was originally retailed by a small provincial supplier, Sisson & Parker of Nottingham, and at £25 it felt like I might well be overpaying for it. What finally persuaded me to commit was the unusual styling of the instruments and the quirky push-fit socket design of the compass inserts. It also looked like there might be some kind of imprint on the compass, just discernible in the rather poor photos. The fact that the set was complete sealed the deal.
When it arrived, the first thing I noticed was that the blurry imprint was the word “PATENT”, but unfortunately there were no other identifying marks. My first thought was that the patent might apply to the socket design, which works on essentially the same principle as Riefler’s round system inserts, but the opposite way around with the male fitting on the compass leg. All the parts are matched to the compass, stamped with the number 33.
However, the real surprise came when I opened the compass to remove the pencil insert. Far from being the standard long joint usually found on these instruments, the head was a self-centering design; but the biggest surprise of all was that, behind what looked like a simple pivot joint, it actually used a version of Lotter’s gear mechanism, patented in 1911. The main feature of Lotter’s patent is the steel plate with its double countersunk sockets to keep the legs precisely in alignment. Lotter had used a self-centering geared head before the patent, probably going all the way back to the first parallel compass design of 1897.
On the Sisson & Parker example, the steel plate is prominently visible on the front of the compass as a sharp projection that sits in a recess formed at the top of the legs. The screw heads are almost completely concealed, but can just be seen beneath the main pivot of the handle. In this respect, the arrangement most closely resembles that of the original Parallelzirkel Gebrauchsmuster (linked to above).
Although the handle itself is much more in the style of the other imported student sets, there is something about the form of the legs and their cross section that is reminiscent of the earlier Lotter compasses. Furthermore, Lotter are known to have dabbled in push-fit compass inserts, which can be spotted in their pre-war catalogues and revisited in the round system Telesco sets of the 1950s.
Far from being an open-and-shut case, this raises more questions than I am currently in a position to answer. It is not at all certain that the set was made by Lotter, nor even that the “PATENT” imprint refers to Lotter’s geared head. Even though the steel plate is clearly that of the 1911 patent, it might have been fabricated after its expiry from around 1926 onwards. My feeling is that the set is earlier, but even this does not rule out another fabricator having licensed the patent from Lotter. On the other hand, could it be possible that Lotter – whose early signed sets are very thin on the ground – was secretly manufacturing large quantities of anonymous sets for export? Perhaps this set is the missing link! It would be good to hear any thoughts on the matter.
