Thanks, AnnabelMore and Phy!
I am obviously looking for insights by outsiders, and all thoughtful comments are welcome. I am not so much looking for "dating" advice as for pointers as to how to behave in the poly world so that I can function more effectively in it. And who knows, some of what I say may also resonate with others. In a world where "The Big Bang Theory" is a hit, I am clearly not the only person with predicaments such as mine.
On dating, I don't particularly want to date at all - in my experience it is a highly unnatural activity. It would be best to bypass it altogether. Within two or three weeks of meeting my wife, we were not dating any more, we were just together in most of our free time, as if we were meant to be that way. We even stopped keeping our finances apart, it was too much of a bother.
But, realistically, it is unlikely to happen like that in a new poly relationship, for how else can two people get to know each other? I am retired and I don't (aside from going to poly meetings) engage in many activities where I get to meet the same people over and over again. So, should I meet someone (in person or online) even remotely compatible, I will have to ask her to get together for coffee, a walk in the park, a movie, and what are these if not dates?
AnnabelMore, indeed my wife had met others willing to take the plunge, in fact she was wary of such people. But our meeting was a once-in-the-lifetime experience, unlikely to happen again. Should it happen with someone else, I will be delighted, but for now I would be happy with a nice easy-going girlfriend even if the compatibility factor is not in the stratospheres.
Of course, one likely possibility is a partner who is already in one or more existing relationships. But how to even start talking to such a person? The typical pattern I see is for women to come to poly meetings with a partner who seems to be quite protective. They sit together, they react to others like any other couple in a social setting. I know it's my attitudes that have to change here, but I find it hard to imagine how to go up to someone with a husband/boyfriend nearby and say "Hey, we seem to have something in common, would you like to have coffee with me sometime?".
And since most such suggestions are likely to be met with a (possibly friendly) no, I will have to relearn to deal with rejection, not a pleasant emotion at all. After all, most men my age play golf or something...