In April 2016, updated Patient Information Leaflets for Mercury Pharma levothyroxine tablets were posted on the Electronic Medicines Compendium site. The dates within the documents are November 2015. At the same time, I think, they updated the company name to Concordia International on EMC (but not on the documents themselves).
The reason I am posting is to highlight that the actual tablets themselves are changing.
The old tablets were marked FW41 (for 25 micrograms), FW21 (50 micrograms) and FW31 (100 micrograms). A rather odd and seemingly haphazard identification scheme.
The new markings are LT on one side and 25, 50 or 100 on the other side.
This does seem to be a more rational marking scheme (assuming LT is being used as an abbreviation for "levothyroxine").
[The same changes were also made to the documents for the product when packaged with the Eltroxin branding - which is not available in the UK.]