My partner bought this pen at an antique stall in Angel, London.

Hi,

Very strange although not unheard of, both pens (and other models) came in that design, from memory they are pretty much the same size, but the 27 has a wide cap band rather than a narrow one, nib may be different, but I'm not sure.

Andy

Thanks for the reply.

The pen has a wider band so it can be a 27.

cheers.