Garate, Anitua y Cia was one of the better manufacturers of handguns and supplied the British with approximately 45,000 copies of the S&W New Model 3 top break revolvers chambered for the .455 Webley cartrlidge in WWI.
Davez, unless your revolver was marked .32-20, I'm guessing that you have a one of the 8mm Lebel (8.3x27.5mm) revolvers made for the French in WWI.
Several manufacturers supplied the French with 8mm Lebel revolvers and the 8mm chambering was moderately popular in the commercial market as well.
I found what I thought was a .32-20 S&W M&P copy made by Trocaola, Aranzaba, y Cia at a gun show for $20.00 several years ago . There were no markings indicating caliber on the gun.
I took my prize home and loaded it with .32-20 light reloads. Upon firing, I found the accuracy miserable and the fired cases, like yours, were no longer bottle-necked, but a straight taper.
I measured the chamber and the bore and determined, after lengthy research, that I had a revolver chambered for lthe 8mm Lebel (8.3x27.5mm)
cartridge that was produced for the French in WWI (see The Illustrated Encyclopedia of Handguns by Zhuk and Spanish Handguns by Ganagrosa).
Trocaola, Aranzabal y Cia along with Garate, Anitua y Cia was considered one of the better Spanish manufacturers.
The 8mm Lebel cartridge was originally loaded with black powder and original pressures were in the 18,000 psi range
Using Nonte's the Home Guide To Cartriddge Conversions, I shortened .32-20
brass to the appropiate length. The bore diameter is 0.327". I made a compression die and bumped up Lee 308-100-2R (100 grain) cast bullets to 0.327".
I loaded the bullets over 1.5 grains of Bullseye or 2.5 grains of Unique (.32 S&W Long data from Lee's Modern Reloading). These loads are mild (below 10,000 CUP) and give plinking accuracy at 25 yards.
My revolver is a fun gun to load for and shoot and the price was right.