Note, this will contain possible spoilers for Deacon's conversation. For those of you who do not know, Deacon is one of the Railroad, a rather extreme pro-Synth freedom group. He has a penchant for changing his face. He will initiate at most 3 conversations with you. The first, he claims to be a Synth, even giving you a recall code. You can call him out on this and he says he might be lying. The second, he says he founded the Railroad, along with some others, and that he's over forty years old, somewhere in his seventies I think. Again, you call say that's BS, and once again, he says he might be lying. The third time you do this, he says he's had to for awhile now, that its part of his job.
Now, my question to you all is, do you believe he's lying? In any of his statements I mean, his backstories as it is. Him being a synth could allow him to found the Railroad, as Synths generally don't tend to age. What do you guys believe? Is Deacon a Synth? Is he almost a hundred? Or is he one big phony?
When you say his 'recall phrase' he just laughs which throws one off the synth scent... but is that a diversion? I don't think the almost a hundred thing is true... his level of ability would only make sense if he was an older synth; problem is, the Broken Mask thing in Diamond City happened in 2229 and was a prototype that failed. From that, it's safe to assume a proper Gen 3 like H2 wouldn't appear until later, so assuming they perfect the model only 5 years later he would only be 53 at most (if he is a synth at all).
He cares a lot about the Railroad, and since their history is pretty much unknown it's still a possibility that he could be a founder. In 2277 they only send one member to monitor the Capital Wasteland, suggesting at that point they are still somewhat weak, so Deacon founding it slightly earlier isn't impossible.
TL;DR --> Almost 100? Nah. Synth? Possibly. Founder? In my books, somewhat likely.