That's not exactly what Scott wrote:

The only surefire ways to know if it's enhanced (originally or not) are to look at the serial number (anything made in April 1986 or later is an "e") or to see if an 800K disk will work in its drive.

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He said the only surefire way, and I agree with him on that point as the case backs are often switched out and internals changed. Also, the only difference between a 512K that was upgraded to a 512Ke, is the missing "d, e, or ed" from the Agency Label, but that doesn't make it any less a 512Ke, or variant.

Anyway, for those who want to know more, try searching the forum for "512Ke" and you'll find a plethora of details discussing the history of this odd critter.