GBG, I cannot imagine why you would act anonymously. Either the gun is registered, or was at least in the old system, or it ain't. Either way, the CFO will likely allow it to be registered, and transfered. If, eventually, the CFO denies registration, transfer, etc. you are going to have to give the gun up. Although executors can take quite a while settling an estate, and outstanding items like this gun are a prime example of why it can take so long, eventually, it must be resolved. You cannot delay performing your duty in a reasonably expedient manner in order to defy the intent of the law. Well, you probably can, but not properly. Sooner or later, the gun has to get a warm safe home.
Everyone here can advise you on the legal risks of neglecting to regularize this gun, while continuing to possess it irregularly. Odds are extraordinarily low that you would run afoul of the law, but the penalties of so doing can be extraordinarily extreme. A Criminal Code conviction in regard to possession of an unregistered handgun could net a 10 year firearms prohibition, as well as the inconvenience of a criminal record if you want to enter the U.S.
Of course, coming on a firearms website, asking about dealing with an unregistered restricted weapon greatly increases the odds that you will also encounteer difficulties with the law.