Identification by Serial Number
Now more likely than not you have struck out on your attempts to identify your light plant by model number. Your next step is to try to identify your light plant by serial number. Look for a riveted tag on the side of your light plant, this is your serial number. If you see two tiny holes where the tag was or the number is illegibly, there still might be some hope by referring to the visual identification guide. Any numbers cast into components such as the crank case are of no value for identification purposes.
July 1, 1916 to January 1, 1922 - With Prefixes
Up until January 1, 1922 each model light plant had a separate series of consecutive serial numbers. The following prefixes were used up to serial number 7000:
| Prefix | Model Number | Prefix | Model Number |
| A | 303 | K | Old 1250 |
| B | 301 | (1,000 watt) | |
| C | 304 | L | Old 1278 |
| D | 302 | T | Old 600 |
| G | Engines Only | No Prefix | 850 |
Serial numbers arranged alphabetically by prefix.
No Prefix - Model 850 Plants
| July 1, 1916 | 1000 |
| January 1, 1917 | 9500 |
| July 1, 1917 | 21000 |
| January 1, 1918 | 36000 |
| July 1, 1918 | 50000 |
| January 1, 1919 | 63000 |
| July 1, 1919 | 73000 |
| January 1, 1920 | 94000 |
| July 1, 1920 | 110000 |
| January 1, 1921 | 112000 |
| July 1, 1921 | 116000 |
"A" Prefix - Model 303 Plants (2 1/2 K.W., 32 volt)
| July 1, 1916 | 1000 |
| January 1, 1917 | 9500 |
| July 1, 1917 | 21000 |
| January 1, 1918 | 36000 |
| July 1, 1918 | 50000 |
| January 1, 1919 | 63000 |
| July 1, 1919 | 73000 |
| January 1, 1920 | 94000 |
| July 1, 1920 | 110000 |
| January 1, 1921 | 112000 |
| July 1, 1921 | 116000 |
"B" Prefix - Model 301 Plants
| January 1, 1918 | B100 |
| July 1, 1918 | B400 |
| January 1, 1919 | B900 |
| July 1, 1919 | B1600 |
| January 1, 1920 | B2500 |
| July 1, 1920 | B3200 |
| January 1, 1921 | B3400 |
| July 1, 1921 | B3700 |
"C" No Prefix - Model 304 Plants
| January 1, 1919 | C100 |
| July 1, 1921 | 116000 |
"D" Prefix - Model 302 Plants
| January 1, 1920 | D100 |
| July 1, 1920 | D600 |
| January 1, 1921 | D1000 |
| July 1, 1921 | D2000 |
"G" Prefix - Gas Engines
| July 1, 1919 | G100 |
| January 1, 1919 | G200 |
"K" Prefix - 16 Volt, 300 Watt
| January 1, 1921 | K100 |
| July 1, 1921 | K300 |
1 K.W. Plant - Old 1250
| January 1, 1920 | K100 |
| July 1, 1920 | K200 |
| January 1, 1921 | K3000 |
| July 1, 1921 | K3900 |
| January 1, 1922 | K5300 |
"L" Prefix - Pulley Plant Model 1278
| January 1, 1921 | L100 |
| July 1, 1921 | L400 |
"T" Prefix - 600 Watt Plants
| July 1, 1920 | T100 |
| January 1, 1921 | T4400 |
| July 1, 1921 | T5600 |
| January 1, 1922 | T6500 |
From January 1, 1922 to July 1, 1931 (serial numbers 150,000
to 355,100) all plants were numbered consecutively as they left the factory –
regardless of the model number of the light plant. It is impossible to identify the model number of a
Delco-Light plant from these serial numbers. Serial numbers had to be referenced to the distributor’s
card file of owners or to the Delco-Light General Office in Detroit to
determine the model number. To my knowledge, from conversations with the General Motors Heritage Center and Kettering Archives, these records have been lost.
| January 1, 1922 | 150000 |
| July 1, 1922 | 160000 |
| January 1, 1923 | 170000 |
| July 1, 1923 | 184000 |
| January 1, 1924 | 199500 |
| July 1, 1924 | 208300 |
| January 1, 1925 | 219220 |
| July 1, 1925 | 229400 |
| January 1, 1926 | 242000 |
| July 1, 1926 | 255000 |
| January 1, 1927 | 278000 |
| July 1, 1927 | 296300 |
| January 1, 1928 | 303600 |
| July 1, 1928 | 313600 |
| January 1, 1929 | 324072 |
| July 1, 1929 | 333386 |
| January 1, 1930 | 346200 |
| July 1, 1930 | 351800 |
| January 1, 1931 | 353000 |
| July 1, 1931 | 355100 |
From July 31, 1931on Engine-generators had the following prefixes to serial numbers for purposes of identification. (Serial numbers 355101 and up)
| Prefix | Model Number | Prefix | Model Number |
| A | 8A3 | G | 15C3 |
| AI | 8GAB3 | H | 15H1 |
| B | 8BK3 | HJ | 50HD1 |
| BI | 8GB3 | I | 6G3 |
| C | 8C3 | J | 50AD1 |
| D | 15FA1 | L | 8G3 |
| E | 15B1 | M | 8M3 |
| F | 15C1 | WI | 8GW3 |