The 6.5 is a rare barrel length n the 27 line. Never cataloged they just pop up from time to time. I have one from 1956 and I have heard they appear through the engineering changes up until the early 1970s then they stop showing up.
Yours have the ramp sight or the Patridge? Seems about evenly split. I wanted the ramp and it took me a long time to find one and I paid through the nose for it.