Dublin Central Tramways Company
The Dublin Central Tramways Company operated horse trams for just over 2 years - from March 1879 to July 1881 - following which, the company, along with the other two city centre tramways (the Dublin Tramways Company and the North Dublin Street Tramways Company) was subsumed into the newly formed Dublin United Tramways Company. Photographs which unequivocally date from the above period appear not to have survived, so it is currently impossible to say with any degree of certainty whether or not horsecar crews wore uniforms, or for that matter, any other form of official insignia such as badges or licences. However, given that the successor company - the DUTCo - did not see fit to issue uniforms to its staff until the advent of electrified services, some 15+ years later, it seems highly likely that staff of the DCTCo simply wore informal attire: jackets, shirt and ties, and the fashionable headgear of the day, in all probability the bowler hat.
For a short history of this system, see: Through Streets Broad and Narrow' by Michael Corcoran; Midland Publishing (2000).