The HBRs were a series of receivers designed by the late
Ted Crosby, W6TC and published in QST during the late
50s and early 60s.

The design used plug-in coils for the osc and rf stages, and
they were double conversion designs, with a first IF of
1600 kc and a second IF of either 100 kc or 85 kc (when
using surplus ARC-5 IFTs.) The 1800 mc xtal you bought
your dad was used for the second coversion osc. to convert
the 1600 kc IF down to 100 kc. Many hams deviated from
the exact original IF frequencies (i.e. strong local BC
station on 1600 kc) which might explain why the xtal
was chosen for 1800 kc instead of 1500 or 1700.

I'm gathering parts to build a more updated version, using
half-lattice filters salvaged from Heath HR-10 receivers for a
first IF at 1682 kc.

Pete