I can't remember.... But I believe that Holmes tore a page out of the November 1963 issue of Guns and Ammo, (dept 472) and took that page to Capt Fritz early Saturday morning. Holmes said that he had discovered the ad and wanted to tell the investigators where the arch villain Lee Harrvey Osssssald ( booooo Hisss) had bought the rifle.
I believe that is BS!..... Holmes definitely was watching Lee Oswald's PO box ( at the request of the FBI) and he knew exactly where that rifle had came from. If we were to know the truth...We might find that it was Harry Holmes who told the FBI where to look to find evidence that the stinkin little murderin commie had got the rifle.
When Gary Savage wrote "1st Day Evidence " he presented copies of the photos and documents that the DPD had at the time they were working the case. On page 248 / 249 Savage presents the page that Harry Holme tore out of the Guns and Ammo magazine .... Both the Carcano and the snub noe .38 pistol are circled in that Klein add.
I’m going by memory, so I could be off by a bit. But Carl Day rode back to his office with an FBI agent on 11/22/63 when he took the rifle to the evidence room. And the FBI agent obtained the serial number, etc. during the trip. So, by mid-afternoon the FBI was able to start tracking down where the rifle came from. There was only one gun shop in Dallas that had sold that make of rifle. The serial number didn’t match any that they had sold. However, the FBI did obtain the name and address of the importer. The importer traced the serial number as being sold to Klein’s Sporting Goods in Chicago. And by about 10:15 pm or so on 11/22/63 the FBI had Klein's employees looking for information regarding who they sold it to.
If Holmes took his advertisement to DPD on Saturday morning, it appears that it was of little or no benefit to the FBI.