My newest cat (aptly named Trouble) has been here for almost two years. Bobbin still has to sleep in the bathroom and go out during the day to avoid him. I think if Bobbin would just smack him a good one, he’d back off, but Bobbin is a chicken and won’t take him on. They both seem happy enough with the arrangement, though.
So people would know that they were neutered/spayed ferals. It prevents duplication of effort (so that other rescuers don’t try to pick them up to be neutered/spayed again…for females, especially, it can be tought to recognize a long-past spaying until the vet has already made the cut).
It lets other people who see them know that they’ve already been spayed/neutered.
Thanks JayJay and Freudian. I had no idea that that was customary.
Cats is strange, and there’s no telling how it will end.
My story:
My Maggie and Turk used to get on fine.
Then they got separated for about a year during my disaster of an engagement. They’ve now been back together about a year and are only *now *no longer hissing and spitting at one another, but they still aren’t as comfortable with one another as they had been TWO years ago.
Now, add in my 12 week old kitten - Widget - who has been in residence for about eight weeks. At the moment, Turk, at age 9, pretty much ignores her with the occasional, half-assed hiss or two. Maggie, much younger than Turk, had begun to play somewhat with her, with rather less hissing and complaining.
Right now, Widget is still overnight at the vet’s after getting her big operation. When I bring her back home tomorrow with all new smells, etc., on her, it will be very interesting to see if anything has shifted in the balance of power between herself and Maggie.
I swear, taking Turk in to be groomed before I brought him back home, changed Maggie’s attitude toward him - and not for the better. It’s gotta be the smell.
We shall see. If push comes to shove, and because I can’t put Widget in a bath after her spaying and de-clawing, I’ll throw Maggie in and scrub her fuzzy butt to change the smell.
That’ll take the wind out of her sails in a heartbeat. 
In my only personal experience introducing a new cat into a home where there was already a cat it took just about six weeks.
I’ve posted about it before. When my husband moved in I already had a male cat who was about eight years old. He had a one year old female. He brought her and then went to Kansas City for two weeks. She spent that entire time underneath my bed. Closing the bedroom door to separate them would’ve blocked access to the litter box for one of them. They just growled for about three solid weeks. Then they only hissed when they accidentally ended up within a few feet of eachother.
Eventually (after, as I said, about six weeks total) they became friends and would lounge on the same piece of furniture at the same time. But the older cat was definitely in charge.
To put it simply, cats are like middle school girls. 
There’s about a 5-year age difference between my two, though I had the younger one first. They still fight and chase each other, but not as much as they used to. And when they’re through fighting, they start grooming each other . . . which often leads to another fight. All in all they get along as well as can be expected, but the first few months were a little crazy.