This page lists and covers the entire range of GEC's Small Oxford lantern, as the range is fairly extensive and telling them apart can be very difficult from the outside. This range includes the: Z5543B for 125W MBF/V, Z5545SB and Z5555SB for 60W-200W GLS (BC), Z5546SB and Z5556SB for 80W-125W MB/V, Z5547SB and Z5557SB for 60W-200W GLS (ES), Z5548B and Z5558B for 45W SO/V, and the Z5549B and Z5559B for 80W MBF/V. Thank you to Simon Cornwell's site for this information.

Loughborough

The Charnwood Museum in Loughborough possesses a GEC Small Oxford, mounted to an ornate wall-bracket which also supports the sign at the main entrance.

The notch for correctly aligning the refractor is clearly visible from this angle:

A view from further away provided an excellent side-profile, and I'd imagine that this lantern is still in use, given it's position at the entrance to the museum. It's very possible it was installed new from GEC back in the day, as it is not listed as an asset on Charnwood Museum or Leicester County Council's websites. Nowadays, it has aged into an artefact itself!