Small engine specs, decoded.

A real EXi / 550EX-725EX Series stamp, read part by part:

• Model: 104M02 - The six-character model stamp. The first two characters are the displacement class in the Briggs numerical designation system (10 = the ~10 cu in class; this engine's actual swept volume is 163cc). The remaining characters encode the basic design series and the crankshaft orientation / PTO / starter configuration group. On modern stamps some positions are letters (here M) - the letter is part of the model exactly as stamped and must be copied character for character.
• Type (first four digits): 0196 - The type pins down the exact build: for 0196-F1 the manufacturer documents 163cc, 7.25 gross torque, a 25 mm x 3-5/32 in crankshaft drilled and tapped 3/8-24 with a 1/4 in keyway, ReadyStart, and a 3,200 rpm maximum. The sibling type 0197-F1 is the same engine with a 7/8 in shaft instead of 25 mm - which is why a model number alone can never spec a repower.
• Type suffix: F1 - The letter-number suffix completes the type: it marks the trim/assembly revision level of that type. A different suffix can mean a different carburetor, tank or control set on the same four-digit type.
• Code: Code (third stamped line, format YYMMDD + assembly suffix) - The code is the build stamp: its first six digits are the build date in year-month-day order, followed by digits/letters identifying the assembly plant and line. The code is what a dealer uses to apply date-sensitive parts changes, so quote it when a parts list splits by code. (No individual engine's real code is published here - codes are unique to each engine and must be read off the stamp.)

The full EXi / 550EX-725EX Series decode guide - or open the decoder with your own stamp.