Maybe a spacer between yhe trigger group and the grip frame. . Maybe a engineering after thought glued in and not a " part " so to say.
Looking at a hw"40" this looked close but I s just a long shot there used in each model or a clue ???
View attachment 576386 Like marflow i looked at lots and nothing . Even forums with pictures of one dissembled / nothing ..
Sorry
It kinda looks plastic so i figured a grip/frame spacer or insert (???)
This much took apart and shows nothing on that
Had this one for a while and started leaking air. Total rebuild of orings and good to go. Airguns of AZ wanted well over 100 to do this and said you need special tools.... Yea right hold my beer watch this. You just have to dive in. This is one of the things I enjoy with these complex airguns.
www.airgunnation.com