I've just completed my run of the Yaffa/Page Publications Conan the Barbarian series so here's a cover gallery of my copies with some notes:
The first issue was published late 1977 with a $0.50 cover price. The indicia confirms 1977, and the rear cover advertises the Fantastic Four series @$0.35 an issue. Given the first issue of Fantastic Four was cover dated October 1977 it indicates this Conan series began October or later.
The second issue was published 1978 as per the indicia with a $0.50 cover price. My copy suffers from dodgy cropping, hence the white sliver at the top of the book.
The third issue was also published in 1978 with a price increase to $0.60. MAY is written on the rear cover by an adult hand, presumably by the newsagent, so it appears this issue was published March 1978.
The fourth issue was published 1979 as per the indicia with a $0.60 cover price, and was the last full-sized issue before the digest-sized issues took over.
The fifth issue was published the following year in 1980 as per the indicia and maintained the $0.60 cover price. The number 8 is written in pen on the front cover, and the rear cover advertises The Incredible Hulk The Movie, both of which indicate this issue was published circa June 1980.
The sixth issue was also published in 1980 with a $0.60 cover price.
The seventh issue was published circa April 1981 - the number 6 is written in pen, presumably by the newsagent. As I understand it, notations by newsagents indicated a sell-by date, that is, the shelf life of a magazine, not the on-sale date.
The ninth issue was published in 1981 according to the indicia, and the cover price is increased to $0.75. There is a 1 written in pen on the cover, suggesting a sell-by date of January 1982, therefore suggesting a publication date of November 1981.
The final issue is a regular-sized reprint of the first issue - an established pattern for many Yaffa series - with a $1.10 cover price. As per #10 there is no indicia date.
Given #9 was published November 1981, and had a sell-by date of January 1982, it is not unreasonable to assume that this issue, and probably #10, were published, or at least on sale well into 1982. I mentioned in a recent post that I'm finding evidence that Yaffa's Marvel reprints ended in 1982, not 1981 as I previously thought, and this goes into the evidence box. The facsimile reprinting of earlier editions does smack of an end-of-licence last gasp gesture, whether in 1981 or 1982.
My thanks to James for his contributions to this dating issue. I'm going to follow up on a lead of his which may help provide some answers. TBC.
Update: Given new evidence to hand - that Yaffa digests were published in 1984, and that the sell-by date is likely two months after the on-sale date, I have revised some of the information above after the initial posting.