Thompson "Tiger"?
See Thompson images at www.oldengine.org/shows/Chilton Engine Specs:

• 4" bore with 5 1/2" stroke
• Flywheels 19 1/2 diameter with 1 7/8 faces
• Spark plug ignition
• Gas mixer has a diamond symbol with a capital "L"
• "exhaust" port at rear of cylinder is open to combustion chamber at bottom of piston stroke

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