Window Balance Stamp Codes Explained
A stamp helps identify the spring strength or calibration. It usually does not identify the complete balance series.
What can a stamp tell you?
A legacy pattern such as 25 3 may correspond to a 2530-style strength option. Mappings can have exceptions, and old rating systems vary. Treat any normalized code as a calibration clue, not a guaranteed weight or series label.
Do not interpret the leading number as a direct sash-weight value. Stamp codes are calibration clues, not literal weight labels.
Why two balances with the same stamp can still be different
Two balances may use the same spring calibration while having different top fittings, bottom fittings, or shoe depth. That is why the stamp cannot choose between S380-compatible and S385-compatible configurations on its own.
When the stamp is unusual
Record unusual suffixes, DS markings, incomplete text, and non-standard codes exactly as shown. Compare the metal channel length, channel width, fitting shapes, shoe depth, and—when interpretation is uncertain—the sash weight.
Related guidance
How to measure a window channel balance · S380 vs S385: the shoe-depth difference
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