2 columns in my road are 1970s Stanton and Staveley CS1805 columns, now fitted with sleeves.
Following the failure of the lamp in the Beta 5 of one of them, I was luckily enough to catch Balfour Beatty when they came to relamp it. The friendly operative was kind enough to share the following info.
The backboard confirms the column as mid 1970s - my house dates from 1978, and the column is a couple of years older - 3rd July 1975.
Note circular cut out near top of right edge of door aperture. These are normally filled with a concrete plug. They are in fact a safety indicator for the state of the column. As the steel reinforcing bars rust, they expand and this pops the plug out. If its missing, it means the column is due for replacement.
Sure enough , the rebar is corroded.
Just visible in the base of the column is the plug - inside red square.
So it looks like this columns and its neighbour will soon be replaced -it probably won't see its 40th birthday.
The green sticker on the backboard is the Southern Electric (as it was then) safety test - 1997.