This digest-sized Yaffa issue of Kid Colt Outlaw does not have an issue number, nor a cover price, so I have always deemed it an unnumbered issue similar to many one-off recycled digests issued by Yaffa after the original run of the series expired.
I now believe it is #5 in the series, incorrectly unnumbered and also missing the cover price due to a printing or editing error.
The first indication of this is the 1981 indicia date, which sets it in the first phase of the Yaffa Marvel digest editions,
The second indication is that it fits in the gap in the Ausreprints.com cover gallery between #4 and #6. Kid Colt Outlaw #4 is a $0.60 issue, Kid Colt Outlaw #6 is a $0.70 issue. And assuming these issues were published in sequence, then a comparison with the Grand Comics Database cover gallery for the Kid Colt Outlaw series confirms this issue belongs between the covers selected for the Yaffa issues #4 and #6.
I'll be on the lookout for a legitimately unnumbered $0.75 recycled edition.
Speaking of which, I expect that the digest-sized Wild West Action is the unnumbered retitled edition of Kid Colt Outlaw #3 which is also missing from the Ausreprints.com cover gallery. I assume that this is a regular-sized issue but it's possible that it is a digest-sized issue. I look forward to pairing Wild West Action with Kid Colt Outlaw #3 and adding them to my Yaffa gallery of such pairings, which does include Kid Colt Outlaw #2 paired with Kid Colt Evens The Odds .
Update: I can confirm Wild West Action is indeed a reprint of Kid Colt Outlaw #3, a digest-sized issue.