There was at least one design of combined B1/B3 antenna like you describe, though not all of them had the "delta-wing" swept-back style (this was probably more based on marketing than RF theory!)
The usual approach was that the boom part was actually a transmission-line and both the elements of the "H" were connected to the antenna feedpoint, one set directly the other via the transmission-line, in the style of the "ZL Special" or "HB9CV" 2-element beams used by us amateur-radio types.
On B3 it would work like the HB9CV/ZL and provide a bit of gain/directivity; on B1 one pair of elements would have been largely irrelevant, the other pair would be a 'short' dipole brought up to resonance by the transmission-line boom, and probably be a few dB down on an undistorted dipole.
Alternatively could it have been something like this:
http://www.wrightsaerials.co.uk/aeri...ient/019.shtml
--G6Tanuki