[turretslug]

I'd wondered if a former rugby commentator had had another string to his bow, too, but I think it's yet another harmless and inconsequential piece of Far Eastern English (aka Chinglish, though not restricted to Chinese-made stuff). Even highly-respected makers came up with the occasional howler.

It looks like the sort of thing that Astec made, Marconi would have taken a bit of care over something like this, especially if they hoped to supply the MoD as they did with so much stuff.