I wouldn't guess it's original, but there were many Boler
plants, and no guarantee that they used the same parts or even that any one of them always used the same parts... maybe one day they ran out and some guy picked a coupler up at the local hardware store.
Since most people are not fanatic about originality, the main concern to me would be whether or not the coupler is a safe and sound design. Likely yes (this stuff is generally tested to industry standards so any brand is likely fine), so as long as you know how to use it properly, and it is in good condition, it should be fine.
tends to use a handwheel type of coupler with an interesting feature: the clamping part underneath which is pulled up by the handwheel to engage the ball has four faces, shaped to match different sizes of ball (typically 1-7/8", 2", and 2-1/8"; yes, I know, no one has a 2-1/8" ball...). If this coupler is that multi-fit style, and you don't have it turned the right way for your ball, it may not be properly secured.
This is from one of the current U-Haul
user guides; bizarrely, it does not mention that the clamp has differently sized faces, although that feature has been described elsewhere, and is apparent in the drawing.
has a very different coupler from Atwood.