Triumph used the letter W as the pre-fix for wheel parts until they computerised their system around 1973.

The W then became the number 37- and shorter suffixes were converted to 4 digits by adding leading zeroes.

Therefore, a part designated W1237 becomes 37-1237 and a W76 becomes a 37-0076.

The parts referred to under either system are generally interchangeable
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Stocked parts from Factory Number 37-0003 to 37-7236: