These are designed and made by Plastimo who make compasses for boats. It's a sailors hand bearing compass. The standard version comes in blue and is a lot cheaper than the green version that is marketed by traser (you used not to be able to get a green one direct from Plastimo, only from traser / H2 with tritium illumination that the one from plastimo doesn't have so this explained the £20 price difference.
If this is plastimo and £34 quid, does it have tritium lights or is it just luminous ?
Tony has actually reviewed this on the BCUK site (as opposed to the forum).
They're big, very good for taking bearings, have a flexible bottom to the oil capsule so that you don't get bubbles in with the needle when the weather changes.
I haven't used one but have had a look in the shop. It's a very specific purpose tool - used on a yacht where you need to take hand bearings for navigation. Can't do this with a bulkhead compass. Walking compasses - even the best - aren't big, bright or stable enough. This is.
Lastly - you have a chart table on a yacht so bearings are always transferred to the chart with a plotter / parallel rules or the like. The compass never gets put on the chart so doesn't need a protractor base.
I've never seen the traser version of this any less than £50. If his is, I must go and look again ! If it's not tritium, then £35 is the going rate from lots of online ships chandlers.
EDIT - just checked - it's the standard luminous one now in a range of colors. Good kit, good value but tritium would be nice on something like this that may well live in the dark, not round your neck, and be "flat" when you need it to check the bearing of a lighthouse without blinding yourself while you "charge" the compass with your flashlight !