Screws loose, so they tightened them with improper drivers.
Billy Bob trigger job.
To clean the action.
Something was/is wrong and they fixed/attempted to fix the problem.
Robbing parts. On Colt's with target hammers it's not uncommon for the hammer to have been robbed for another gun.
This isn't really an issue on a Detective Special, unless someone had cut the hammer spur off, and a later owner wanted to put it back in original condition.
Last, who know? Make up a reason, and someone will have thought it a good idea at the time.
Numrich has some sideplate screws. Some are sold out. Don't know what the difference is.
I have had the sideplate off every Colt I have except one NIB. Why? Most of the above. Many/most at least casual owners don't. Therefore most are gunked, a little or dirty, or not lubed at all. I want to know. So, I have in various cases inspected, cleaned, lubed, totally disassembled and reassembled (that's the important part) and yes, even repaired. Sorry about that. I can't imagine someone interested in a piece of machinery like a gun who wouldn't want to know it was clean and well lubed and didn't show signs of excessive wear at least if it was a shooter. But that's just me. /forums/images/graemlins/grin.gif
I should add that all mine are more modern D frames and therefore perhaps not as complicated or tricky as some - or as valuable.
I 1st got addicted to Colts because of the machinery. I've had the side plate off of one gun (that I no longer own). A gun can be messed up very quickly with a unexperienced person and I'm not talk'n about the screws. Too bad the person that messed up these screws couldn't even use the correct screwdriver tip.
I should confess that I bought one very rough DS for the sole purpose of a project gun, something to disassemble and perhaps repair if necessary and perhaps have refinished if it is adequately functional. I'm having fun with it and learning a lot. It is one gun that I don't have to worry about handling - I can't hurt it. Perhaps everyone has already done something like that at some time or other, but if not, I think it is a good idea.