It’s a two-panel Hagar the Horrible in which Hagar says “There are little flecks of gold in my beard. Don’t they make me look distinguished?” His wife replies deadpan “Those are codfish flakes.”
I know it was printed prior to 15 June 1975, but not very long before. I could have found it myself earlier in (I think) the Go Comics archive, but they seem to have changed their format. 
If you’re able to narrow down the range, you could try Google’s newspaper archive.
Here’s Hagar for April 7, 1975. (April 6 and 7 were combined into one scan.)
Thank you! 
Glad to help.
I used to read Random Acts of Nancy and, when possible, track down the original strip; the archive for the Pittsburgh Press is one of the resources I used.
Here is the June 15, 1975 strip:
Then you can scroll down from there to look at the days prior to this. But I went all the way back to the beginning of May, glancing over every comic, and didn’t see anything that matched the story you are looking for.
This comic was before my time but wouldn’t silver or gray flecks make more sense for beards and Atlantic fish?
The reason I remember it so well is that my beard at the time did have gold flecks in it, something my girlfriend commented on the week of 15 June, right after her birthday. Referencing the cartoon, I told her they were codfish flakes.
I did the same in the Cleveland Plain Dealer archives and did not see anything that matches the description. Memory can be a fickle thing; there might be some detail that’s not quite as you remember it?
I’ve gone through the first half of 1975 and not found it. The strip debuted on 4 February 1973, so there’s a little less than two additional years to search.
I am 100% sure of the details, I just don’t remember on what day I saw the strip. It couldn’t have been much earlier than 15 June 1975 because it came to mind so quickly.
Silly comic strip, not documentary. 
I found a Facebook post where someone wrote the following:
“There’s a comic strip in which Hagar is proud of his beard, which is turning silver due to his age. It turns out they’re actually fish scales.”
That’s possible, but the flecks in my beard at age 20 were definitely gold.
Fish scales makes so much more sense and approaches funny! Last night when I posted, I actually thought codfish flakes meant bits of a meal of flaky cod Hagar had eaten and didn’t consider fish flakes = fishfood (for pets) till this morning.
I also wondered if the strip showed Hagar admiring gold beard beads(?) that a Viking costume might include, lol.
I’ve looked at a lot of archived strips and can’t find any older than 50 years. The cutoff date seems to be 1 January 1975, which really pisses me off. All of the first two years is simply ignored. 
Judging from where I was living in 1974, it had to have appeared in the second half of that year.
It may be in one of the first few books
I’ve been trying to find a couple of those in my area, but no luck so far. Maybe a Doper or two has them?
My mom taped up a Hagar comic strip on the fridge. Hagar approaches his wife and asks “When do we eat?” She replies with exasperation, “You mean when do you EAT and EAT and EAT and EAT!” Hagar then turns to the reader and says “Gee, I thought they liked to cook.”
That was for my dad, but I don’t he ever noticed it.
This looks like what you need
ABE has a copy for 15 bucks.
I just found the cartoon going through six months of The Pittsburgh Press archives. It appeared on Page 9 of the Saturday, 29 June 1974 edition:
The Pittsburgh Press - Google News Archive Search
Turns out my memory was maybe 98% accurate. Not bad for an old geezer like me! 
Approaches, but I’m still trying to figure out why that’s funny enough that Dik Browne would think “I’ve been working on a joke about fish scales… wouldn’t work for Hi & Lois, but maybe in Hagar’s beard. Aha, I think I’ve finally aced it. It’s certainly worthy of running in major newspapers alongside Peanuts and Doonesbury!”