I got the Simon MP3300 PCB. The solder-side is labeled MB Electronics 4850 Rev F. The only other Simon PCB that I have is the one with the custom IC, which is labeled MB Electronics Milton Bradley PN7924850F02 REV-B. The datecode on the 75494 driver is 7914 on the MP3300 PCB and 8624 on the custom IC PCB. The MP3300 PCB has screw-in bulbs and the custom IC PCB has push-ins.

Here's the info: http://www.seanriddle.com/simon.html