Nick that is a wonderful piece of hardware!
You will want to hydro test and inspect it before you steam it.
Then do a fresh hydro test and inspection every year and keep a test and inspection log.
Most of all.... enjoy it!
Gil
Gas may be best from a corrosion stand point. Coal produces a lot of acid.
I think if you did a leak test with soap and water while inflated with air with the PV valve spitting... You could check all the seams. Any visual signs of corrosion?
I'll know more in a month as I will be at Steam School. 
What pressure does it steam up to?
I have been told it was hydro-tested to 300 psi. I do not know when though... it came with a ton of paperwork that I still need to look at more carefully...
And I will be talking with a few of the instructors at steam school that I know live in MN, and hopefully I can get some help from them...