Winchester magnum rimfire
This Model 676 was equipped from the factory with both a .22lr cylinder and a .22 wmrf cylinder - depending upon condition and barrel length (12" barrel commands a 20% premium) value will range from Excellent - $275 down to Fair - $75.
25-130 USD or so
50-125 or so
50-150 in poor to average condition. In Excellent condtion, with box and both .22lr and .22 magnum cylinders this model has sold in the $300 range.
Best left to a gunsmith
No such model number in the S&W line
I bought mine in 1977.
676 can be written 676 ----- 1
25-75 USD or so
Since 676 can be divided by 2, (676/2 = 338), 676 is an even number.