I'm guessing that 745 would solve the mystery part of this SN?
Anyway, much of the older prefixed serial number data has not yet been entered into the data base. And the even older non-prefixed numbers would be ambiguous unless they change the lookup form to also ask for the model of the gun. Prior to GCA68, Ruger started numbering every model at 1, so there will be multiple models with the same number. For example, there is a serial number 1234 Standard Auto, Single Six, .357 Blackhawk, .44 Blackhawk, Bearcat, Super Blackhawk, Hawkeye pistol, 10/22, Deerstalker, .41 Blackhawk, .30 Blackhawk, and #1 rifle. I might have missed some, but you get the idea. So by itself, Ruger has no way of knowing what model serial number 11745 is.
The feds didn't like that ambiguity, which is why GCA68 specifies that going forward (from 1969) a serial number from a manufacturer must identify one and only one firearm in a known caliber. Ruger complied by adding a serial number prefix that identified the model line (and caliber, at least for the Blackhawks). The double action revolvers were mixed calibers from the start, so a -Six DA might be .38, .357, 9mm, .380 Rim. Same with the Redhawk, GP and SP lines, and beyond. Recently, Ruger has even changed their Blackhawk practice with guns of many calibers being numbered with the 38- prefix. But internal to Ruger, they know what caliber a given number left the factory as and can provide the lookup data to everyone since it is all computerized.
The yearly range tables for models are approximate and should not be considered gospel. There were many reasons for certain individual guns being held back and not shipped in the year expressed in those generalized tables. You would need to get the $10 letter from Ruger to know for sure.
Fun fact: when Ruger fist published the generalized SN range tables, they didn't have their own data compiled into one convenient location. So they took the early tables from Chad Hiddleson's "Red Eagle News Exchange". The two sources may have diverged over the years, but that is where Ruger started.