Perhaps someone else can come up with more information, but I can only say that the gun is of the class called "suicide specials", though it is unclear whether that meant the gun was good for only one shot or that anybody using one against a better armed opponent was committing suicide.
In any event, that type of gun was sold by the millions (literally) in the roughly 1880-1920 era, in calibers .22 and .32, the latter in rimfire and center fire. The prices ranged from under a dollar to $2 or $3 dollars for fancy grips or engraving. There is a mild collector interest, but there were so many such guns made that only those in near new condition are of interest. Even so, they rarely bring over $75; yours is worth much less because of the poor condition.
If it has any sentimental or family value, you could oil it to kill the live rust, then hang it on the wall. It does not even have trade-in value because most gun stores will not give you anything for it without adding that onto the price of what you are buying. (For liability reasons, they can't sell it; they would just scrap it.)
I strongly recommend against firing any modern .22 ammunition in that gun.
It does look like the Pioneer, so you may well have hit it. The only odd thing is that H&A guns, being a cut above most of the "suicide specials", were usually marked in some way. However, my comments above would still apply.
These little cheap pistols were sold by the 1,000 in Sears & Robuck catalogs. They were very popular in the early part of the 20th century. Mail order was legal so you could order one no problem. This gun looks very much like the "Blue Jacket Arms' or perhaps the "Ethan Allen" hard to say. The Aubrey Firearms Co, made many under different names. These guns sold for around $2.00. But the 1900 dollar was worth $22.00 of todays money. They were often called "Saturday Night Specials". Folks out having a good time often needed some protection.
Like one pic shows, only an "S" on the gun. Some other makes and models come close to looking like it but the real tell tale sign is on the hammer, 4th pic. The "pin" is off center to one side, a lot of those were in the center.
I also think that this gun has been redone and the markings were sanded/ground off for a smoother looking piece before it was plated.
Also a lot of them had a lever on the left side for removing the cylinder. The Pioneer is the only one that closely matches the guns configurations so far.
The grip shape is not quite like that of pictures of the Pioneer, but closer than most.
FWIW, not only was it legal to buy guns by mail, but there were very few laws against open or concealed carry. Open carry was common in the west and south, concealed carry in the northeast and mid-west. Everybody carried; bankers and bookkeepers, prostitutes and their customers*, housewives and ministers. President Theodore Roosevelt reportedly once patted his pocket as he was leaving the White House and said, "I have forgotten my pistol, and I have a meeting with the Archbishop in a half-hour." Roosevelt presumably didn't consider the Archbishop as being a danger; carrying a pistol was simply a way of life at the time. Did it eliminate crime? Alas for the pro-gun position, no. So laws were passed to eliminate crime by gun control. Alas for the anti-gun position, they don't work, either.
*Mae West's famous remark, "Is that a pistol in your pocket or are you just glad to see me?" was a reflection on a society that was habitually armed.
That looks very close to those made by AETNA ARMS Co. around circa 1880's vintage.
This company was located in Manhattan.
If you do a Google search you will find some examples.
Their logo of "AETNA" had the letter "E" with no vertical post
The 3 horizontal bars in "E" were attached directly to "A",
so you will see people reading this as "ATNA" as well.
I would search for it with both AETNA & ATNA spellings.
I think I would hide it in the rafters or attic of the house and forget about it. Maybe in a hundred years or so someone will find it and think they have a real treasure. I have an old farm house, built in the 1800s and found part of an old crappy shotgun hidden in the basement. I put it back where I found it.