@Forclaz please post more images of the entire bike with details; e.g. lugs, drain hole, dropouts, seat stay ends. Disregard my comment in your other thread since you have identified year and provided a photo here. I suggest posting threads dedicated to a specific bike (e.g. Colnago Super circa 1978), posting detailed photos, and addressing all issues as they come up.
For reference on my input regarding classic Colnagos I own/have owned or others steel framed Colnagps (I have 8 steel framed Colnagos from 1970-mid '90s, plus a late '80s-early '90s Carbitubo) do search: "keyword" Colnago, "posted by" Jesper
What makes you think it is a 1978 frame other than what a seller stated (need more photos to provide a more accurate assement)? It may be the correct year and a possible repaint since decal style is more 80s than 70s (maybe late '79 like a frame I have). It appears (hard to see in photo) to have internally nutted brake caliper mounting which would suggest later than '78. If it has embellished seat stay endscthan definitely later than 1978 model (though frame may habe been built in '78).
My '78 Super's decals are consistent with the year before the white panel was being used. Note: '78 frames started to adopt the Nuovo Record dropout with mounting holes for the portacatena (chain carrier introduced in 1978 by Campagnolo) component; but it still has unembellished seat stay ends and externally nutted brake caliper mounting; generally '79 and certainly 1980 frames (excepting some lower tier models like "International, Sport, etc.) and later had "COLNAGO" molded into stay plugs, internally nuts for brakes, and white panel decals.
Late '79-early '80 SUPER; factory ordered frame; odd decals
'78 -early '79 Super