The Story on Serial Numbers

Each Alco Firefly Steam Charging Set has two different serial numbers. One is on the nameplate riveted inside the lid of the sheet metal box the generator set is stored in. This number spans all product lines manufactured by Arthur Lyon & Co. with a nameplate attached. While the tag is useful in determining when an item was finished, the nameplate serial conceals production figures for individual product lines.

1944 nameplate with Serial Number 57700, associated with Set ID M 77

1945 nameplate with Serial Number 106850, associated with Set ID 1174

Thankfully, a separate and inconspicuous number exists and it appears to be sequential within the Firefly generator set line. This number, sometimes obscured by paint or a light strike of the stamp, is typically located on the flat part of the engine crankcase across from the crankcase vent. The number may also be stamped on the aluminum sump. A third location where the number may exist is on the generator’s ammeter/fuse box, written in pencil.

Two numbering formats exist. In one, the letter “M” is stamped over a number. In the other, the number is is a four digit number beginning with 1. As we go down our growing list of namplate and inline numbers, the M format appears to have been used intially.

Brendan’s generator set 58316 with engine M 90 is the latest on record here made in 1944. My boiler with serial 58533 is the latest recorded serial from 1944. The first recorded set from 1945 is 58601, which has 1098 penciled on the ammeter box. (If you own this set, please let us know if that number is indeed stamped on the engine.) That generator set is only 68 nameplate serial numbers away from the 1944 boiler, and so it must be very early 1945 production. Chiel purchased generator set 58611 and confirms it has 1081 stamped on the crankcase and sump of the engine – this a major revelation.

Before learning about the existence of engines M 511/M 717, M 533, and 1081 (all thanks to Chiel), my original conclusion was that at the start of 1945, the engine numbering format changed and somewhere between sets 90 and 98, the 1xxx format came into use. So, 1098 represented set number 98. But this is now obviously incorrect.

Chiel owns 1945-dated generator sets 58611 with 1081 stamped on the engine crankcase and sump, and 106996 with M 533 stamped on the engine sump. (Paint obscures what is stamped on the crankcase.) The existence of an engine number under 1091 and above M 97 disproves my conclusion of a numbering format change.

Set 106996 with engine M 533 is only 5 nameplate serial numbers away from set 107001, sold by Preston Services, which has 1261 written on the ammeter box. (Again, we assume that is also stamped on the engine. If you own that set, please confirm.)

It is apparent that both M and 1xxx formats were used concurrently for at least part of the Alco Firefly production run. I would like to see more examples submitted with engine serial numbers from 1001 to 1090, over 1390, and over M 90.

I now think the different formats are actually serial number “blocks” used by two manufacturing teams or suppliers machining and assembling the engines and generators. Identifying small differences in manufacturing method would support this conclusion. For instance, I have seen many ammeter boxes marked in pencil with a 1xxx number, but no M numbered sets with the engine number marked on the ammeter box.

Set ID M 77. Original serial number format stamped on crankcase.

Set ID 1244. Revised serial number format stamped on crankcase.

Set ID M 32. Original serial number format stamped on aluminum sump.

Set ID 1174. Revised serial number format written in pencil on electrical box.

The engine Chiel used to own with crankcase number M 717 and sump number M 511 is an oddity. After the war was won, it was common for war production contracts to be reduced or cancelled outright. Often, companies were left with work in progress components. Could this engine have been assembled with leftover parts? Or were 717+ generator sets indeed built with M numbered engines? If so, based on highest recorded engine numbers (M 717 and 1390), at least 1107 Alco Firefly generator sets were produced.

We have not recorded any non-M-prefix engines below 1000, but could they exist? Perhaps, and that would add 1000 units to the production total, but if the two number formats are indeed serial number blocks, this is unlikely.

More information is required to support conclusions about total production of the Alco Firefly, but we are making progress with each submission. Please contribute to this effort and tell us about your Firefly.