I am familiar with the variability in serial number vs date characteristics of several pistol manutacturers. High Standard has similar yet different issues like the other comapnies and I always recommend the factory records be consulted in preference to generalized charts. My data is based on the factory records but even than generalized data will never be as good as the data for a specific serial number.
The grooving under the rib on your gun is a characteristic of the 5.50" bull barrel found on a catalog number 9263 and is not part of a weight reduction effort. The dovetail at the muzzle end was for the original front sight before the rib was installed.
What book lists the 103 series Supermatic Citation as being produced from 1958 through 1966? It is not correct.
My website www.histandard.info
has the models listed for the various design series for all the types of High Standard firearms. You will note that catalog number 9263 was available beginning at about serial number 1,223,XXX in 1962 in the 103 series and continued through about serial number 1,514,XXX in about 1963. The 104 series version of the catalog number 9263 began about 1964 and continued through 1966 when the catalog number changed to 9244 which was not a change in the pistol itself but was to distinguish the difference caused by the deletion of the previously included accessories in lieu of a price increase. Teh 9244 continued until 1978
The reference you quoted of my post references the Supermatic Citations found in a production lot near the approxmate serial number you originally gave. All guns were using the same serial number series at the time of your gun so pistols derringers and revoolvers are all intermixed in production lots which were scheduled to maintain inventory based on orders received and to level the load in the shop. Lot sizes varied in quantity by the relative popularity of the particular model.
The following image is an image of the factory record on which your pistol appears.
As you can see, all serial numbers do not have a shippping date. Those that do not have the shipping date, account number and invoice number have instead a key serial number, the key serial number for a particular shipment. One must lookup the key serial number to see the ship date, the account number and the invoice number for that shipment.
Shipping destinations for pistols from this time frame are not available except for the pistols made under government contract.
I hope this helps.
The following link is to a catalog page showing the catalog number 9263. http://www.histandard.info/datapubli..._1024_768.html