Copyright status for a recent purchase of a Curwen sheet music

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Hello,

I have recently purchased from Hal Leonard the TTBB arrangement of Swansea Town from Gustav Holst (whose SATB version is already on CPDL). However, the score is a print from Curwen Editions, with a 1924 copyright mention, and Hal Leonard's logo is only put in the very end of the sheet music and no copyright mention from Hal Leonard.
Given that the sheet music was in Tonic Sol-Fa notation, I've edited it in standard staff notation and was considering making it available on CPDL. However, I'm not too sure of the copyright status of that score. Basically,

• I'm guessing that the original score's copyright
• But it's still being sold by Hal Leonard

Am I in the clear to publish it to CPDL?

Thanks in advance for your guidance