A pair of knitting needles, 1940s
Apparently unused with original paper binding still in place.
The needles are made of the featured material, casein formaldehyde. The end pieces are of urea formaldehyde.
Degradation typical of the material not visible in this example
Can crack if kept in too dry conditions.
Casein is a relatively stable plastic but requires higher humidity storage than other materials as water acts as a plasticiser. Storage of these needles in a humid environment might help them straighten out. Unlike with other plastics it would not do any damage.
Display and storage
No special requirements except ideally to be kept in higher humidity than other plastics (e.g. 55-65% RH). Make sure it is not very dry (e.g. under 40% RH).