An IJ is a better gun that the Spanish Alfa. Yours is most likely chambered for .32 S&W. I would use the .32 S&W Short in it if you want to shoot it, but even with the .32 S&W Long, it would not be adequate (IMHO) for serious purposes. (I say this knowing that probably more people became eligible for premature planting from calibers like the .25ACP, .22 rimfire, and .32 S&W than any of the more powerful calibers.)
The IJs, like most older guns, tend to break, and repair costs are often far more than the gun is worth. In fact, many gunsmiths won't touch them because you can spend hours on one and never be able to collect a fair price for the work.
Jim