License Plate Gallery

The Wisconsin Pages:

Understanding Insert Truck and Trailer Plates

Wisconsin's "insert" plates for heavy trucks and trailers are fairly unique, and I find them to be some of the most interesting license plates in existence. They're unusual and colorful in appearance...particularly the light teal 1994-dated baseplates that were in use for many years. They seem "exotic," since they're seldom spotted on anything but commercial machinery. And, they offer an amazingly large plethora of variations...types, weight codes, and die styles spread over continuously-progressing number series.

When did it begin, though? Through the end of the 1930s, heavy and commercial trucks received annual plates identical to those for lighter vehicles. Since registration fees were much higher for heavier vehicles, this was a major inconvenience for heavy truck owners who used their vehicles infrequently or for only a few months out of the year. "Insert" truck plates debuted in 1940, and were introduced to provide the option of quarterly (or in some cases, even monthly) registration to owners. The "insert" nickname was in prosaic reference to the large quarterly metal inserts that validated the plates.

Insert plates were replaced annually through 1971 (by which point actual metal inserts had given way to adhesive validation stickers), and then biannually from 1972 to 1993. The teal 1994-dated baseplate wound up being used for fifteen years, and the current gray base debuted in time for the 2009 validation cycle. Only gray plates should be in use today, although occasionally a straggling 94 will sneak by on the roads.

The first key to understanding these plates is their serial system, which consists of a two-letter prefix followed by numerics. The upper letter of the prefix is a weight class code, while the lower letter is simply a serial character. Weight classes vary from the lightest (X, which is slotted out-of-sequence before D) to the heaviest (T). Trailer plates also encompass three light classes (A, B, C) that fall before X. Lighter weight classes are more common, so the serial ranges for these codes extend higher than for plate series farther along in the alphabet.

92 base

94 base, Type 1

94 base, Type 2

94 base, Type 3 (four-digit)

94 base, Type 3 (five-digit)

09 base

Serials for each weight class series started at A 1. (Other related types like trailer and tractor had their own starting serial letters; specifics are provided in the table below.) Interestingly, the numbering series on insert truck plates has progressed continually since 1992; even though two reissues have taken place since. The 94 baseplate picked up beyond where the 92 serials left off, and the gray plates were likewise a direct continuation of the 94s; as the series of "G"-class plates above make clear.

Initially, the numerics for each prefix started at 1 and worked their way up to 9999 before the serial letter was incremented. After Wisconsin switched to a narrower die set in 1994, they started letting numbers run up to 99999, which slowed down the serial letter progression significantly. (In fact, only two series have advanced a single letter in the system since then.) It also seems that new serial letter series now start at 10001 rather than 1.

Up to 19 weight code series exist, each with its own parallel serial series. Including the 1992, 1994, and 2009 bases, these series are spread over five distinct variations of plates...and in addition to ordinary truck plates, there are tractor plates, trailer plates, heavy farm vehicle plates, farm trailer plates, "Special-UX" plates, and "Special-Z." With all of these multiplications and permutations taken into account, the total number of potential variations is staggering: 478! Many of these permutations are quite rare, and the bulk of what may be seen on the road falls under the realm of 20 to 30 common types.

The following table compiles the serial ranges and break points I have confirmed for post-1992 Insert plates. Not all series or variations are listed. The "expected start" for the 2009 base was rounded off from observations with WisDOT's plate inquiry tool.

License Plates Wisconsin Light Trucks, Other Types Trailers & Heavier Trucks

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©2008-12 Andrew Turnbull.
Last update December 23, 2012.