Does this shape appear in other series?   Yes - Later Series 19 and 500 Series 532 are like 315 s.

Also, elsewhere in the Early Series Early Series 334 is like 315 s, and Early Series 2 is like 315/5.

Five size variants are recorded; s plus inch suffixes 5, 7, 9 & 12. The overall proportions vary between the sizes, more so than usual. On 315 s the flared lip is more prominent relative to the body.

Comparison; the same shape in two different series, 315 s (left) with Later Series 19

Without twig-handle - unusual amongst the larger 315 sizes.

   Height;  9.5 - 10 cm.

Early Series 315 s, 5, 7, 9, & 12.