I recently had a MetroLux (One) come in for repair. It was a very early serial number, the 26th in production. There were issues with reset and the unit seemed to operate very slowly. All other functions performed. We don't get many MetroLuxes (MetroLuxi ?) for repair, they just don't break and I had never seen this before. As bad luck will have it, the percent function had 00 loaded. Don't know how that is possible, but when it happens all bets are off. Restoring this fixed the unit. I discovered that very early ML had no reset, we loaded new units with all the numbers by hand. And finally, the Custom Code Numbers were from 0 - 127, with most of them acting as duplicates.
Bottom line is that if you have a very early unit, you can tell by the Custom Code Number range of 0 - 127. In this case, you have no reset. A good CCN is about 23. See the Q & A and instructions for updates.