There are no published date guides, you can contact kinght directly to find out dates of manufacture. Address in the related links below.
It's on the barrel under the forend. You'll have to remove the forend.
An Australian One Dollar note (Knight/Stone) serial CSY was printed in 1979.
All Australian banknotes have a serial number. For each issue of banknotes, there will be a first and last serial number. The Australian paper Fifty Dollar note issued in 1973 with the signatories Phillips/Wheeler, had a first serial number of YAA 000000. The last note printed in that series had a serial number of YAU 999999. The next series of Australian paper Fifty Dollar note issued in 1976 with the signatories Knight/Wheeler, had a first serial number of YAV 000000. The last note printed in that series had a serial number of YBX 999999. Banknotes with first and last serial numbers usually have a higher collector value.
Australian One Dollar notes with the serial range CPK to DGH inclusive would have been printed in 1979 and signed by Knight and Stone.
In answer to part two of your question, you usually cannot get a new barrel with the same serial number, however; the part of the firearm that must have a serial number is the frame of the firearm. In other words, a replacement barrel with a different serial number is kosher. Many firearms manufacturers will replace the barrel with a new one that has the old serial number along with additional numbers/symbols/letters to indicate it is a replacement as long as you send it to the manufacturer for repair.In answer to the first part, maybe. Without knowing how bad the pits are, and any other possible problems you might not see, it is not possible to give a definitive answer on you case. Consult a gunsmith.There are very few firearms that are serial numbered on the barrel to match the frame/receiver. There is no requirement to have a number on the barrel.
I can not find a date code published by Knight, but you may be able to obtain it from them directly at knightrifles.com
serial number mavis beacon
Serial number.
serial number of thunder
The serial number of the titanic is 16458990231
the serial number is on the back