You don't have to tell me everything about yourself in a query letter. In fact, I'm sure we both prefer you err on the side of less rather than more. There are some places however where less is not in your best interest. Here's one:
You wrote a book. It was published by BigAss & BottomLine Publisher sometime before 1990. Then it went out of print. Then the rights reverted to you. Then you republished it using one of the slick ass template printing companies that call themselves publishers. Places like iUniverse.
Then you tell me only about BA&BL, not the iUniverse, edition.
Every single time you tell me you've been published I look it up. Every single time. No exceptions.
If the only edition I find on Amazon is the iUniverse edition, and there's no hint of the other edition anywhere, I'm not impressed. There are a lot of authors who go out of print but remain for sale. Used book sites, even Amazon, will sell mass market editions of very old books if people want to buy them. When I don't see your book there, I assume people don't want to buy it. That does not bode well.
So, what to do? Get the damn thing OFF Amazon before you query. Unless you're selling a hundred units a month (in which case you mention THAT in your query letter) you probably aren't going to lose much money by delisting it.
Then you also mention why the book can't be found anywhere. Maybe it's a red hot collectors item. Maybe all the stock was destroyed in a fire. Whatever it is mention it.
If you don't tell me, I just assume no one wanted to buy it and all copies are currently living in the FreshKills Landfill on Staten Island. I'm right 99% of the time on this assumption. If you're the exception, you'll need to tell me.