A photo or two would be helpful.

From your description, I am led to believe that your find may possibly be a short-barrel shotgun, illegal without an accompanying special federal tax stamp (among other things).
• Is the attic you mention your own, or someone else's?
• Are the two barrels smooth inside, or do they have internal grooving (rifling)? (If they're grooved, you're OK—it's just a pistol.)

I believe that Aco Fino may mean something like "high-quality steel," since "steel" in Spanish is acero, and in Italian accaiao. Fino means "fine" or "high quality" in both languages. (Aco Fino might also be Portugese, or Brazilian.)
The "450" is probably just the inside diameter of the barrels: 0.45", or .45 caliber. However, it might also be a model number.

If you can make photos, please include all of the markings and stampings that you find underneath the two barrels.
If my conjecture is correct, the barrels come off (to make photography easier) by first removing the fore-end (the wood underneath the barrels).

Pics would be a great help. I the grips curved or straight? Could be a saddle pistol made in Spain from 1870 till about 1910 black powder cartrige. They were for the gentlemen to have on thier saddles for defense. I have seen pictures of them and if it is that type of pistol in is considered antique firearm.

I would love to post pictures but don't know how on this forum. It says I can't send attachments. I did look inside barrels and they are grooved.

Post your photos to Photobucket: https://login.photobucket.com/
Then use Photobucket's system to copy the picture's address and post it here.

If the barrels are rifled, it's all, "No problems, Mate." It's legal.

Pictures by gavyde - Photobucket .....this is it.....if I did it correctly. Let me know what you think. I did get a serial number off the side. Can't locate a brand name on gun though.

1. If you pass your mouse over each separate photo, you will see a list of "codes" in a popup menu appear. Select and copy the IMG (image) code, and paste it to your forum post. Magically, the photo itself will appear within your forum post.

2. I believe that Tony Pasley hit the jackpot: A Spanish saddle pistol. But before we're sure, it'd be nice to see closeups of markings, both atop the barrels and on their bottoms.

I have no idea of its value, yet. Maybe with photos of markings I could pin it down.
If nobody chimes in with more information, you could also try the people at Old Town Station:
Armchair Gun Show, antique guns and collectible firearms for sale
or at
Kull's Old Town Station Firearms Auctions - Live Online Gun Auctions

The only thing stamped on the bottom of the barrels is 2 letters...."DD"....hope this helps

Nope. Nothing like it in my reference books. Sorry.

Could it be "B.B." rather than "DD"? (That would mean that the gun was made in Belgium, rather than in Spain or somewhere else as yet unknown.)

Most (all?) European guns have proofmarks on the bottoms of the barrels, usually very near the breech (where the cartridge goes in). Shields, crossed objects, that sort of thing. That's what I'm looking for.
The basic Belgian proofmark is a tower shape with a widened base that looks a little like a skinny Eiffel Tower.

If you find any proofmarks, please post the information.

I see only one marking....its not on the barrel itself but when I open the gun it is etched on the inside where the barrel rests when closed. The symbol is a small circle with a line coming off of it with a small triangle on end of line. Kind of resembles an arrow. That is all I can see. The serial number is etched on the side of the gun. I appreciate your help.

Nope. Nothing.

The mark you describe reminds me of the symbol for "male." ("Female" is a circle with a cross descending from its very bottom.)
Maybe it's a maker's mark.

Sorry—I can't be of any more assistance.

There are several earlier percussion or pinfire designs that look similar to this; perhaps a copy of one of those? These are the only things I could find that were substantially similar, but as Steve said, there should be some proof marks on it if it were Belgian:

Guns For Sale : Fine European Guns For Sale - .45RIM?? BORE IS GOOD,ACTION WORKS.PIRATES??? - Auction: 8799983 (Ended 09/22/2008, 08:42:49 PST)

45 Belgian Double Pistol

Nice work, DJ Niner! Better Google-fu than I do.

So there you have it.

Maybe Spanish, maybe Belgian, maybe Arabic. Maybe even from India. Not unusual, however. Worth from $300.00 up.

There are these, too, in larger calibers, both suspiciously similar: http://www.lsstuff.com/howdah/577howdah.html

Originally Posted by Steve M1911A1

Nope. Nothing like it in my reference books. Sorry.

Could it be "B.B." rather than "DD"? (That would mean that the gun was made in Belgium, rather than in Spain or somewhere else as yet unknown.)

Most (all?) European guns have proofmarks on the bottoms of the barrels, usually very near the breech (where the cartridge goes in). Shields, crossed objects, that sort of thing. That's what I'm looking for.
The basic Belgian proofmark is a tower shape with a widened base that looks a little like a skinny Eiffel Tower.

If you find any proofmarks, please post the information.

Hello...did a little more digging and found a mark exactly where you said it would be. It is a circle with a crown on top...it has the letters LG below the crown and inside the circle. Also, looks like the letter E above the LG. Also stamped along barrel are the the letters I and C but a few other letters I can not make out. Thinking gun is Belgium. Really want a date of manufacture if you can help. Thanks again.

That's a Belgian proof mark.
Case solved.

The crowned oval containing "E" over "LG" indicates a firearm barrel that has withstood a 50% overcharge of black powder. Belgium required a black-powder proof before trying smokeless in the gun. The marks you have found seem not to include a smokeless-powder proof.

This proof mark has been in continuous use since 1888, so there is no way to date your pistol by this means.