OK
medine.co.uk says
imedi.co.uk
Metformin Tablets 500 mg are white, round, biconvex tablets engraved with “C” on one side and “323” on the other side, available in blister packs of 28, 56 or 84 tablets
So that explains the first box
The second?
Metformin 500mg F/C Tablets (Round Shape) - Summary of Product Characteristics (SmPC) by Sigma Pharmaceuticals PLC (Special Concept Development / RxFarma)
www.medicines.org.uk
Click on pharmaceutical properties to see the description
White coloured, film-coated, round, biconvex tablets embossed '500' on one side (without break score).
Two different manufacturers?