WOOLEY is entirely correct that this is not a falling ax but a tie hackers ax. I have actually used a similar tie hackers ax to hewn some logs for a cabin rebuild. More work that I would like to do again. The head dated from the 1860's to 1880's, correct time frame to have been used in railroad construction. NEOPHYTE, above mentioned that axes were forged not cast, which is mostly correct as I have a couple cheap hatchets that have cast heads. Mine gives all indications of being a forged head, thus in my mind the initials would almost certainly have been an after manufacture addition. Way too much hand work to just be a property owners ID marking IMO. To go back to the railroad theme, if a person got paid per piece, it would make sense to mark your work. Assuming there were falling crews and squaring crews, once the tree was felled and cut to length and delivered to the job sight. Tie hackers would get to work squaring either 1 or 2 sides before tracks could be laid upon them. This accomplished the opportunity to ID your work with a simple 180 degree rotation of your ax makes sense to me. However, I spent 36-year years standing outside in adverse weather, mostly above 8,000 feet elevation so I am quite certain that many of my brain cells received too much frost bite and never recovered.