Welcome to the Forum. If you got the original box with it and if the original end label is still stuck on it, the model number will tell.
RENE says your gun was made in 1969.
There's one known to be factory chrome but it was an early 4 digit serial number.
Doubt it's a factory job and hints that it's not include the roll marks not being even or appearing "filled-in" .... if that makes sense.
If you complete a form and mail it to Ruger they will tell you for certain. I think it's a whopping $10.00 fee.