Attuvian
Though even very similar, how many engines are exactly the same? Even just the ends. If there are not number boards visible through the roundhouse doors, there are probably little distinctions that you can create in inobtrusive locations.
Hi, John,
All my steam goes into the roundhouse pilot-first, as was usual practice for the real ones. Some of the numbering on the rear of the tenders is very small and, for instance, PRR steam alone I have thirty or-so locomotives. From the backside they look pretty similar. Keeping track of thirty-some engine numbers (plus many more for NYC, B&O, Erie and others) is more than I can do by memory.
I assume we're talking DCC here and when I want to select the address it is nearly impossible for me to see, at about a 40-inch distance, those tiny numbers!
I need to have a "cheat sheet" of some kind in order to correctly address the locomotive.
Glad you like the coupler/dowel idea. It is a simple and cheap tool that can really be handy sometimes 
RR_Mel
ED I tried your magnet idea on one of my scratch builts and I’m sold!!!!
Thanks, Mel! It all started when I picked up some PRR catenary supports that I wanted to use for some photo "shoots"
I didn't want the supports permanently mounted so I came up with the idea of sinking 5mm round magnets glued into the sub-roadbed and gluing thin iron strips onto the bottom of the supports.
If I bump one, no big deal, or if I want to remove them completely the magnets are practically invisible being flush with the scenery.
Some years ago I completely un-wound and disassembled an old transformer. I saved the iron plates (They make great flat car loads of rolled steel sheet) so I have these thin pieces of iron which I use to glue (or double-stick, foam tape) to the roof, or the bottom of the catenary poles, etc.
I bought a bunch of various sized magnets from Ebay sellers. Some are maybe 3mm dia x 1mm thick! Others are various rectangle sizes that are nice for building roofs.
Keep the good ideas coming!
Cheers, Ed