Made Special for the RAF 303 Cartridges

[bombdoc]

The WI is the coding for A.P the headstamp - R /|\ L is Royal Laboratories.

Strictly speaking, no.. the W1 is the shortened designation. The original one is "CARTRIDGE, S.A., ARMOUR PIERCING, .303-INCH, W Mark I". The W indicates the design code.

The official indication of an AP round is the green varnish in the cap annulus. (purple for ball, red for tracer)

If this round is packaged for aircraft use, it is actually "CARTRIDGE, S.A., ARMOUR PIERCING, .303-INCH, W Mark I, SPL". introduced in 1934 and differed from the standard one by having a higher tolerance on length and having the glazeboard wad replaced by a strawboard one to reduced engine damage if it was ingested. It was the standard AP round during WW2. You can tell this is a "Special" as the date is stamped in full.