Two more Protimeter serial numbers for the collection: 285-657 and 443-285.
There are significant differences between these two instruments so there are more variants to be considered.
There are two switch settings: on the 1957 meter, these are marked "Check" and "Test", while on the 1958 version the markings are "Reset" and "Test".
There is also a strange difference between the "Brick" scales. On the earlier meter, there is a short green sector, up to the 18% mark on the "Timber" scale and the legend "Dry" up to the "20" mark. On the later meter, the green segment is badly faded but is marked "Damp" so it would seem that by 1958 there was no dry brick.
Scans of the instruction cards which each meter had in the lid of their cases are attached. Note that the cards state that spare prods are available from "the makers". To the user this would have meant Protim but the "Avominor" legend moulded into the front panel may have been a bit confusing, assuming the user knew of the existance of AVO/ACWEECO.
I had always assumed that these meters were custom made by AVO for Protim. The serial numbers certainly suggest that hundreds of them were made and, without removing the internal back panel, they look professionally produced. My inclination is to think that they were made by AVO.
The use of the Universal Avominor case some time after the Multiminor was in production also suggests that the Protometer design was drawn up some time in the early 1950s.
Companies were probably less hasty to scrap tooling as soon as its main product ended manufacture than now, and it would seem the Universal Avominor tooling still existed in the later 1950s.
It seems that Protim still exist, though now amalgamated with Koppers -
https://www.kopperspc.eu/products/protim.html and trading as Protim Solignum Ltd, Fieldhouse Lane, Marlow, Bucks, SL7 1LS.
You can still buy a Protometer, althought he form has changed a bit. However, the AVO cased version does appear in the literature;
https://www.protimeter.com/assets/do...052419-web.pdf.
Clearly Gerald Gobert, needs some more research.
PMM