The 17 minute short sees the detective doctor duo investigate a murder at a manor in Phwitterby On Thames, but takes the form of a musical comedy with the majority of dialogue being spoken in rhyme form. What also makes it notable is the use of being shot in colour which was still not the norm at the time.
But here is where we are left with our own mystery to solve, the picture you see alongside the autograph is obviously of Pangborn dressed as Sherlock Holmes - not Watson.
Howard came across it while reading a 1928 copy of "Movie Makers Magazine" and it reportedly was from a Pathe-Demille production of a Sherlock Holmes film, at this time we are unsure as to whether this film was ever released or any further details from it. But never one to be beaten by a Sherlock Holmes media mystery Howard is continuing his research to try and establish further facts on the situation.
In the mean time though you can see Pangborn in action from this clip for "My Grandfathers Clock".