The original 1A regulators were in TO-3 cases.
Since the linear monolithic regulator first appeared it has grown to
encompass many and varied versions and packages. I will disregard all
but the original versions in this discussion.
Around 1970-71, before the 78/79 series appeared on the scene Natsemi
had the LM340 series +VE regulator series which were available in both
TO220 and TO3 cases. And before this Natsemi had the LM309 fixed 5V
reg in both TO39 and TO3 cases. Bob Dobkin who worked for Natsemi was
credited as the inventor of the monolithic linear voltage regulator.
http://www.elecdesign.com/Articles/Index.cfm?AD=1&ArticleID=2851
Subsequent to the LM340 series - around 1972 - Natsemi released the
-VE equivalents to the LM340 series as the LM320 series, however these
were only in the TO39 and TO3 cases initially, and sometime later they
were available in the TO220 case. Both LM340 and 320 versions were
eventually available in TO39, TO220 and TO3 packages (and also smd).
I think I am correct in saying that the 78/79 series series
regulators, came after the 340/320 series and were subsequently
manufactured by Natsemi, Fairchild, Motorola and many others, and
became accepted as the industry standard types. The internal circuitry
of the original 78/79 series was almost identical to the original
340/320 series and today Natsemi uses a common datasheet which
includes both types. This seems to indicate they are now internally
exactly the same.