It is normally stamped on the barrel. If it is not, take it to a gunsmith. The smith can use a gauge or micrometer to measure the bore diameter, and tell you the right size ball and patch to use.
rM ROD FOR BLACK POWDER WEAPON
Check the on line auctions.
There were thousands of black powder guns made in Spain in any given year. These range from very cheap to well made. You did not give us much information to work on- whether it is a rifle, shotgun, pistol, or cannon.
Can range from 100-1000 USD
Go to the website of the MAKER of your rifle (Hawken is a style, not a brand). You should find an owner's manual you can download, or request a paper copy for free.
You will have to call TC to find out.
Blue Book of Gun Values, Standard Encylopedia of Firearms are places to start.
Rifle primers are generally not reccommended for muzzle loading firearms- the flame is not large enough to reliably ignite black powder or Pyrodex. There are nipples that use a #209 shotgun primer, and even then, it is reccommended that you use a primer intended for black powder. Check with Dixie Gun works for a nipple that will fit your rifle.
You will need a professional appraisal
i need a hammer for my jukar spain 45 cal serial # 097443
I have one.
In most cases the only way to tell is if the company is still around. You can contact them with the # and get at least an date range. Some of the Spanish guns have a date suffix in the serial number ( 12-123456789-95) would be a 1995 manufacture. Others you can determine by when the model was made and compare it to the number made and have a guess at the year. One book may help, The blue book of modern black powder values has some good information, and may answer the question.