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Ruger has never disclosed how many of any model the produced. They do occasionally give an approximate number, or in the case of special distributor models, the distributor will release how many they will be offering.
As for when it was made, and the serial number not being on the website. The website is NOT the most accurate data on shipping dates. We all use the Red Eagle News Exchange reference guide to help us. Post the serial number & we can offer what we know. But the most accurate way of getting a SHIPPING date is from Ruger Records. Call 603-863-3300, ask for "Records" and then provide the nice lady that answers with the model info & serial number & she will give you a month & year of shipping. They can even send you a letter with that info for free!
Next, post the model info (Example; 10/22RB-XYZ) That too will help us identify the gun. The more details we get,,, the better we can help!