I agree with
@Phil Coffins . I had one of those when I was in my early teens. We still have it in the family. I had a lot of fun with it, and actually killed some squirrels with it.
However, these were very cheaply made. The bore was drilled but not reamed smooth. It has a patent breech, and the breech plug threads were just tapped into the end of the bore, with no counterbore. The nipple was a poor fit, and my dad drilled out the nipple seat and retapped it. The trigger had about a 90 pound pull, which dad was also able to fix by stoning the tumbler/sear engagement. We also fabricated and soldered a ramrod pipe onto the barrel, as the original "ramrod" was essentially a piece of heavy wire with a button on the end. I made a hickory ramrod for it.
So, my dad got it for me as a teaching tool, to show me how to do all of the above. A secondary motive for his purchase was if this gun kept me occupied, I would be less likely to damage one of his originals when unsupervised. With all of that in mind, this gun played an important part in my early muzzleloading experience. However, these were
cheap guns, even back then. Cheap to buy and cheaply made. I don't know that I would pick one up now if I found it in the road. I've seen used but shootable T/C Hawkens for $350 - $400. So, $300 for one of these Spanish rough-bores? I wouldn't.
Notchy Bob