$1300 ! Wow ! I paid $200 for mine in 1978-here in the USA of course.
Not a Colt expert, the "billboard" designation is new to me. I have heard about the collet bushing breaking, hasn't happened to me-yet.
I find a small letter slide for mine, had to use a tiny amount of valve grinding compound to get it to fit.
Lately I have fired mine only with a Ciener conversion unit. Which I recommend.