An example of the last mentioned type of double can be found on the Heym web site.

eg

88 BS / Safari left barrel 7x65 R, .308 Win, .30-06, 30 R Blaser, 8x57 I(R)S, 8x75 RS, 9,3x74 R, 375 Fl. Mag. N.E., .375 H&H Mag.

88 BS / Safari right barrel .375 Fl. Mag. N.E., 375 H&H Mag., .416 Rigby, .450 N.E., .458 Win. Mag., .470 N.E., .500/.416 N.E, .500 N.E.

or

80 BS left barrel .22 Hornet, .222 Rem. Mag., 5,6x50 (R) Mag., 5,6x52 R, 6x70 R

80 BS right barrel 6,5x57 (R), 6,5x65 (R) RWS, 7x57 (R), 7x65 R, .308 Win, .30-06, 30 R Blaser, 8x57 I(R)S, 8x75 RS, 9,3x74 R, 375 Fl. Mag. N.E.

http://www.heym-waffenfabrik.de/english/S_Buechs/S_DopBue/st_DopBu.html