Nixter,
The Ruger Number 3 was discontinued in the late 1980's due to soaring manufacturing costs. According to my friend with contacts in the industry, Ruger actually LOST money selling the Number 3 since the middle-1980's!
The action is ferociously strong (same as the Number 1) but with a simplified block-dropping finger lever styled like the old Winchester/Browning M1885. It was made in 22" carbine length barrels only in .22 Hornet, .223, .30-40 Krag, .375 Winchester, .44 Magnum, .45-70, and a few other calibers. All that I've shot are finely accurate, and subject to the same accurizing "tricks" as the Ruger Number 1.
No doubt the Leopold 'scope is a fine one, but that $600 price seems sorta high at first look. I paid $325 for my .375 Win Number 3 in April.
On the other hand, like-new Number 1 rifles start at Well over $500 now, so it may be a good buy. The action is a good one for rebarreling to classic BPCR calibers, but the hammerless feature leaves it out of NRA sanctioned competitions.
The Ruger site gives serial-number and date of manufacture if you want to look it up.