I don’t immediately recognize it. It might be an A and B with the cross at the centerline (similar to how the Latin Æ dipthong is written), but purely a guess.
From the larger picture it looks like it might have been some type of scout or club uniform given the capes, neck kerchief, and other accoutrement. The emblem almost lost like it is on a waist sash or something distinct from the short pants they are wearing.
I think in this case context (where, when) would be needed as it doesn’t appear to be a widely used Christogram.