The E88CC is a special quality double triode. The transposition of the figures from the end of the type designation to the middle was Philips way of denoting a special quality build.
The E88CC and the very similar ECC88 found great use in oscilloscopes of the early 1960s. This frame-grid double triode was not designed for operation such that it would be at cut-off for long periods of time.
The Special Quality nature of the valve is proclaimed twice. Note the gold plated pins.
The double mica sheets to confer vibration resistance can be seen clearly.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 48 mm tall.
References: Data-sheet & 1040. Type E88CC was first introduced in 1958.