This material is becoming increasingly rare, and was from the mezzanine area of the Conway Stewart Factory sale when it closed it's doors. The material is probably from the late 1970'2 early 80's. Casein is made using milk proteins and is one of the very first types of plastic. It takes a wonderful shine but has to be treated with respect as it is a hydroscopic material.
These pens are very light, weighing in at around 16g without the cap. It will be fitted with a JoWo nib of your choice, just advise me once purchased. Your choices are EF, F, M, B, 1..1mm stub, 1.5mm stub available in polished stainless or two tone (stainless steel). Gold available as an extra in F, M, B. It comes with a quality ink converter and will also accept standard international ink cartridges (not supplied. The pen will come in my branded box.
Please state your nib requirement in the comment section of your PayPal payment.