Ken, your illustrations are awesome! I don't know how you achieve that but they are really nice!
Mark,
Frigidaire downgraded it's model lines at the end of the seventies and model numbers used in the late seventies are quite confusing! Not speaking about the 3 other "parallel" series which had about the same features as the MOL models of the regular line: the Crown (with control panel design very similar to the ones of the regular series with woodgrain/black panels but the black parts being replaced by silver trim and the addition of window lids), the Custom (with different-looking controls and more woodgrain/ less black trim than the regular models) or WS series (with another different design of brown<span style="font-size: small;">-(not woodgrain!)</span>/silver panels and window lids like the Crown).
So about the regular series (with the woodgrain/large area of black controls from 1975-79):
The 3speed WCI was discontinued at the end of 1976 calendar year and replaced by the WIC and WIC-A. The WIC was exactly the same as the previous WCI but the lid switch was moved from the hinge to above the (still bed of nails) lint filter. I think the WIC was discontinued soon after it's introduction and the WIC-A with the same features less the 3 speed motor replaced it.
The 1978 documentation I have recently downloaded from this site doesn't mention your exact model but 4 models for 1978, the WD-A 16lbs model, the WC which has the same features as your WIB and the later (1979) WIG, the WID which has a "fabrics" selector just like the previous WIA and like the later WCIB and (1979)WCIG and the WIC-A which is almost unchanged from 1977 (changes during production were I think, the switch from shaded to non shaded colors and maybe the lint and filter and fabric softener dispenser styles). Somewhere between 1978 and 1979, they replaced the WIC-A by the Elite, the WID was renamed WCIB and WCIG and the WC was renamed WIB and WIG. So it seems they changed model numbers more than once a year but changes between some models are hard to tell. Custom Deluxe models became Imperials, Imperial models became Custom Imperials and Custom Imperials became Elite...