My GG-GF Henry Harder, and his brother Charles Harder were both "Firemen" in Brooklyn from 1870's through early 1900's. I contacted the NYFD to see if they had any records. I found out they were not actual Firemen, as we know them today. Instead they were "in charge of the fires on board steamships or locomotives". Both my ancestors worked on the Ferry, listed on various census as Ferry Fireman and Engineer. I was also told they had to be issued a license to perform their duties.
My question is what Type of License or record set would I be looking for,
and who would I contact to inquire about such a license?
Any suggestions would be appreciated. Thanks in advance.