QST, Apr 1972, p. 142.
QST. Apr 1973, p. 150: This ad shows an external "receiving VFO."
QST, Mar 1974, p. 133. (also shows the VFO)
IC-21A
QST, Oct 1974, p. 131
The IC-21A can be used with the DV-21.
QST, Aug 1975, p. 5.
QST, Apr 1976, p. 81.
References
Review. 73, Jan 1972, p. 27.