This is a genuine tube
line tile, it is unfortunate that one has to
stress genuine but increasingly tiles are being
described as tube lined when they are moulded.
This is widespread on eBay even from sellers who
should know better, sellers who have more than
one tile to compare, and many sellers do not
revise their descriptions even when notified by
other eBay members.
More unfortunately recent literature has
confused the issue. Barnard and Lockett both
make a single tube line error as far as I can
recall, Austwick makes none, Fowler and Harvey
several but the book is very poor anyway so
should be discounted. Of more concern are
Blanchett's volumes, very useful books and a lot
of good information but therein several moulded
tiles are described as tube lined. In the vast
majority of cases it is a simple matter to
determine if a tile is moulded or tube lined,
some pointers can be found here.