Not all of these are entirely British pens. The very slender pen with two gold bands and an accommodation clip is an entirely US-made Mabie, Todd & Bard, doubtless imported when the British branch of the company was being set up. Two others have New York nibs, though the rest of the pen was made in Britain.
The black flat-topped pen to the right is a Swan Leverless Eternal and it has a rigid nib. All the rest are flexible to some degree and the two long eyedropper fillers at the bottom are real wet noodles.
Hi Sem. Would you happen to know why my #58 doesn't have the "Duro" on the nib that most seem to have? Its a flex medium nib that simply says Conway Stewart 14ct Gold. The pen is the early one with a two line imprint. Tiger's eye plastic.
Conway Stewart 58s seem to have been produced in both versions, with or without the Duro nib. Like many matters Conway Stewart, the reasoning behind this will probably remain a mystery. Perhaps they just used up the stock in hand at the time; it may even have been a customer choice though that seems rather less likely to me. Either way, it's likely that your 58 is completely original.