Quote from Bas PAYNE on October 5, 2020, 3:05 pm

Yannisl:

Yes - many possibilities and few clear answers ....

As regards date-stamps and time of posting,  my guess is that pillar-boxes weren't in common use at that time (1883-1893) -  they probably came in quite quickly once rates reduced and became more uniform in 1895. Again, railway mail probably wasn't all that common in 1883-93.  But I don't know of any very solid evidence for either.