The 1AP5/P11 is a small flat faced instrument cathode-ray tube. It is probably from the 1950s and the P11 phosphor indicates a blue trace.
The anchor logo for the US Navy. Made in USA.
The faceplate is completely flat.
The 12 pin duodecal base.
The phosphor is 30 mm diameter.
The end window envelope is 36 mm in diameter, and excluding the B12A base pins is 91 mm tall.
Reference: Observation. Type 1AP5/P11 was first introduced in 1951. See also 1951 adverts.
Updated May 26, 2019.