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SLIDE RULE MANUAL

1957

Below, the last page of the 1957 manual, a partial listing of the Relay "DOUBLE STAR" line up. I say partial, because for example I own a model B-506 not shown here. Also, the 150 was already in production. But here it is, and it is interesting to compare it to the 1959 model line up.

Here's another significant find. This manual came with a tiny little pocket slide rule, model T-401. This manual not only contains a catalog on it's last page, but an explanation of model designations, as seen below. This explains some of the weird numbers seen on older Relay rules, for example the OMEGA DT-1065. Now, we clearly know what that was. And this means also that the 151 was in production before we thought it was. This manual shows several types with which we are already familiar ( 550, 152, 153, 151, 158) yet oddly omits the 150 ( a 1953 is in my collection.) Also, why these model numbers when Relay was already using the above listed model no's before this? Many rules exist before the date of this catalog, with the much more familiar numbers seen in the 1959 catalog. More to research again!

Perhaps Relay re-numbered for a very brief time, or perhaps they devised a different numbering scheme for exported rules. Whatever the reason, it certainly didn't last, as one look at our 1959 catalog will show. This manual is significant because it predates the wide scale import of these rules to the USA. Dated rules from 1956 and 58 do exist here, but are quite rare, while those '59 and later are the norm. Enjoy!

Note that the designation system provides prefixes for many more rule types than are listed in the catalog below. For instance, "K" and "S" aren't used at all, but one would imagine they existed.

Slide rules and their leather cases from this series do indeed have two stars, one on either side of the "Relay" name, just as on the front of the manual. Rules and cases known to have been made just after this series merely deleted the stars, and used the new (old?) model numbers.

Note the use of both Pi folded and sq.root of 10 folded scales. The business and beginner types seem to use the sq. rt of 10 type, with the engineering rules having pi folded scales.

We currently know of rules from 53, and several from 56 using the "1959" model numbers, and a slew of them 59 and later. Just how long this 1957 scheme was used is entirely unclear.