The rifle is marked as a Mk I and it has both Mk I and I* bolt head release systems, plus with the 6L s/n makes me think that it was either a bottom of the barrel receiver, it had a problem and was worked into the system later in production or was used as a trials/pattern receiver for the Mk I* conversion and then put into the system in early '42. If it only could talk.

Thanks for the wood update, one day I will bring it to a wood expert and get their opinion.