Have a bit of a mystery going here. I noticed a marking on the side of a Bally ST in a FB for sale ad that looked a lot like the marking that is on mine, which I had assumed was some sort of graffiti or something an op had put on it. We found another ST here in Houston has the same type of mark, and when I looked on IPDB, there it was again. The mark is EST followed by a 5 digit number, so probably (Something)StarTrek followed by the serial number, since there were 16k units made (see pics).
Anyone have any info on what and why these are?