I acquired this recently, can anyone tell me what it is? The centre section is a length of aluminium tube 135mm (approx 5.3") long, its external diameter is 28mm, and internal diameter is 22mm. It has a thread on the forward end that extendeds 15mm down the outside of the tube. The fins are semi rigid blue plastic and are held on by a steel circlip. One fin looks to have been torn off. What is this? I guess it would be part of some kind of TP munition due to its blue colour. There are no markings of any kind. My thoughts are that this is the tail section of a rifle grenage or mortar of some kind. I however did think it could be part of some sort of civilian item such as an avalanche control rocket.