For engraving mistakes or re-entries perhaps (just an amateur I am, perhaps the upper finials or swirls and lower ones would be interesting also.
The upper left finial has only two curved lines while the right hand side one has three lines present, or indeed a fully drawn on finished burr or reflection to the finial.

The lower left finial has a round dot within it, while the right hand side one has upwards lines drawn.

Perhaps these upwards lines on the right hand side are a style of the KGV era stamps where that side of stamps seemed to have an uplifting to the upwards right so as to leave the impression of a good feeling and that your post through the mails (and mythical ethers?) is indeed on it's way?