not that I know anything about these pieces, but thought the following, quoted from Jackson, might be of interest.............
Described in the book as "Angular mould-blown soda glass...... lightweight turn mould-blown".................. but of more interest perhaps is the entry from the Glossary for 'turn mould-blown', which reads..........."Smooth-sided mould into which molten glass is blown whilst being spun round on the blowing iron"
As would be expected, the rim would need finishing after detaching from the blowing iron, and this is done, usually, by attaching the pontil rod to the base, which in turn needs to be ground/polished to remove the scar.
Presumably more difficult to spin the heavier lead crystal examples, as opposed to the soda glass pieces - just possibly might imply that these lighter ones could have their rims finished by being held in some way other than on a pontil rod.
?
"Whitefriars Glass - The Art of James Powell & Sons' - Edited by Leslie Jackson - 1996......... pp. 136 and 152 (reference to plate 48 is in error - should read plate 148).