The Mystery of the Dagger Carvings on Stone 11

In the 1950s  Richard Atkinson during his excavations at Stonehenge, when the axe and dagger carvings on the stones were first being recognised, photographed Stone 11 and noted and highlighted  five axe carvings on it. The photograph is generically dated 1 Jan 1958 and is in the Historic England Archive:

Close-Up Of Dagger Carvings On Stone 11 Part of the Series: ATK01/01 R J Atkinson photographs. Reference: P50839  It is not available online, only in the archive.

My sketch of the dagger carvings on the South Side of Stone 11 based on the photo:

He doesn't mention them in his book about the excavations, and the 2012 Laser Scan of the Stones did not spot them, and whilst it looked at and judged other possible carvings it seems not to have looked for these.

So a mystery. Are they real? One to look for on a visit to the stones.