This was not Jipcho's first fast 2-day double of 1973.
Jipcho had previously run a World Record 8:13.91 steeple at Helsinki on 6/27/73, followed by a 3:36.6 for 3rd in the 1500 (behind Bayi and Wottle) the next day.
But on July 24, he did a 1-day double at the Bislett Games in Oslo, winning 1500m in 3:37.0 and the 5000 in 13:34.6. (And then he ran 8:16.38 for 2 miles the next day, narrowly losing to Emiel Puttemans).
This was better (on the Portuguese Scoring Tables then in common use) than Steve Prefontaine's mile/3-mile double of 3:56.8 and 13:06.4 on Apr. 15 earlier in 1973 (races c. 1 hr. apart).
Jipcho did lots of 2-day doubles, 1-day doubles, and running many races in a short time period.
See the following link for a career race chronology:http://thegreatdistancerunners.de/BenjaminJipcho.html
Jipcho's "record" for the best 1-day 1500/5000 double lasted for nearly 25 years.
On June 12, 1997, the day before the 100th anniversary of Paavo Nurmi, Paul Bitok won the 1500m at the Paavo Nurmi Games in Turku, Finland in 3:36.87 and 75 minutes later won the 5000m in 13:26.25.
This was to commemorate Nurmi's great 1500/5000 doubles of 1924, the first in June --2 world records; the second in July --2 Olympic gold medals.
Ironically, according to one report, "Even though Bitok competed in two races the way Nurmi did some 70 years ago, he admitted he had never even heard of the Finnish star."
Purely based on times, the best 1500/5000 double was Mo Farah's 3:34.66/13:12.54 wins at the Oxy meet on 5/18/2012.