I have an L579 single shot bolt action.....first one I've seen..dates to 1960.

How common are these?

quite uncommon. FN made a mauser in a single shot too around the same time period. they're uncommon too

The only one I've actually held in my hands was an L-46 that came from, coincidentally enough, Alberta in the vicinity of Calgary in 1966.
Regards, Joe

Heard of them back in the day, but never saw one. Gonna' keep it?

As I recall it, the Sako and FN bolt action single-shots were a market reaction to the then becoming popular re-invented sport of benchrest.

Folks were just starting to learn the advantages from the bench of rigid stocks, actions, and barrels. With the single shot actions, both the action and the stock were stiffened by the lack of a magazine cut-out.

In those days, one still occasionally still saw surplus Mauser actioned rifles in things like .219 Donaldson Wasp, even .220 Swift, WINNING the occasional BR match.

But the .222 Remington had been on the line 6-10 years, and was becoming about as dominant as the 6 PPC is today... So the days of the larger Mauser-type single shot actions were both numbered and generally short-lived.

The single shot bolt actions still make up into great varmint rifle actions, though.....