Very few women at 53 would be looking for casual. No reason to even mention this.
I don't understand why a man would want to get into an LTR with a woman over 50. You don't get her best years. She's well past her prime.
I am able to understand why a man would want to remain in a relationship with a 53 year old woman if he's spent the last 20+ years with her. If a man is in a relationship with 53 year old woman and he started seeing her when she was 30, he got at least some decent years with her.
When she's 53, her looks and youth are gone. She might even still have a teenaged child leftover from a past relationship. Even if a 53 year old woman has all of her kids over age 18, there's a good chance that her kids are 18-25 and might still require some hands on parenting and/or still live at home. Dating a woman with adult children is no bargain either. Blended families with adult children are not good experiences either. That's true for both the older people in the couple and their adult children.
The older women get over the age of 45 or so, the less willing they are to be on board for casual sex.
Why do you think that is?
Instead of saying you are only looking for something casual tell her you are looking for someone that checks all the boxes but aren't jumping into anything right away. This covers all the bases and doesn't blow yourself out. At least this way you can get a few lays out of her.
I agree with this strategy. Being vague is good.
I can think of another time in life where being vague about intentions is good.
For men who don't want kids, it's not advisable to tell women that you don't want kids, especially when dealing with women 24-39. If you're vague about stuff, you can at least some lays out of it. A lot of 24-39 year old women will eliminate a man who doesn't want kids or has a vasectomy based on not wanting kids or not being able to have kids in the future.