Could an Ideal No.5 made for .45 Smith & Wesson be case of mistaken identity? Consider this...
Ideal No.3, Second Variation (1888-1892), as identified in Vol.1 of "Antique Reloading Tools of the Black Powder Era" by Tom Rowe and Ed Curtis.
This tool, which appears to be a scaled-down No.5 (or perhaps the No.5 was a scaled-up No.3), was advertised in Stevens, Marlin, Colt, and Merwin & Hulbert catalogs and is found in a variety of calibers from those manufacturers. It would not be too much of a stretch to suppose it might also have been special ordered for .45 Smith & Wesson. The first image below is from Marlin's 1888 catalog.
Seen alone, it would be easy to mistake this variation of the No.3 for a No.5. When viewed side-by-side, the size difference becomes obvious. The No.5 is a large tool, most suitable for rifle-size cartridges, while the No.3 is more appropriate for revolver-size. Another not-so-obvious difference is that in the No.3 the bullet sizer hole is located in the same handle as the seating chamber, while in the No.5 the sizer in in the opposite handle. Second and third images compare the No.3 (marked .38 W.C.F., with a muzzle resizing die, at the bottom) and No.5 (marked .45 GOV., with optional seating chamber for 500-grain bullet, at the top).
Jim