Actually, it may be allowed even by today's standards.
From the IAAF Advertising Regulations:
4.1.2.7 Clubs/Individual Sponsors
(When relevant, only applicable in respect of international
athletics meetings held under IAAF Rules 1.1(d), (e), (h), (i) and
(j) in the event that such meetings are sanctioned by
organisations that do not have their own advertising
regulations.)
Either the club name or the club Sponsor or the club logo or
the logo of an athlete’s individual sponsor, may be displayed on
the front of the vest/leotard on the right chest.
Such display shall be rectangular in shape, with a maximum
size of 40cm2
and with the lettering a maximum height of 4cm if
printed directly onto the vest/leotard or the size of the patch.
The club name may appear on the back of the vest/leotard with
the lettering a maximum height of 4cm, and no restriction in
width.
Club logos which are part of traditional club names and have
been registered as such with an IAAF Member Federation prior
to 1 January 1980 and without relation to a company or product
shall remain and the size may not be increased. Club logos
including a Logo or lettering representing a company or
product are subject to the dimension as stated under this
Clause.