The wood on that old Selmer C is in incredible condition for its age - if it had been a Bb, it would've been far more worn out looking. I've got a ring keyed Selmer basset horn from this era. I missed out on a Selmer Series 9 full Boehm C clarinet, only because the seller wasn't prepared to ship it to the UK. I then found a Couesnon (stamped Masspacher) C clarinet and rebuilt it as well as adding extra keywork to it so it now has the LH forked Eb/Bb mechanism and a LH Ab/Eb lever. While it's noticeably longer than a Leblanc LL or Noblet Artist C clarinet, it plays slightly sharper. The funny thing is the barrel sockets are both the same diameter, so the barrel can be flipped over.