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Your son has an AUTO EJECTING 2ND Model 3rd Var. Serial number with 'E' prefix indicates production in 1900 or 1901. With a 4 digit serial - most likely made in 1900.
The Model and variation was made to handle BLACK POWDER loadings only. Does the serial number appear on the butt of the grip frame?
Standard issue was 3 1/4" barrel with Nickel plate and black hard rubber grip panels. Optional: 2", 4", 5" and 6" barrels; blued finish; checkered walnut, mother-of-pearl or ivory grip panels. 5 shot .38 S&W (BP) or 6 shot .32 S&W (BP).