Colt Model 1903 Pocket Hammerless .32 ACP serial number 4 - pistol is the earliest known serial numbered example of this model.  This gun contains Belgian proof marks on the frame, slide and barrel of a cursive "L" in a flaming bomb.  This mark is found on barrels and the most important parts of the action of all firearms not made in Belgium and which do not carry proof marks recognized by the Belgian proof house; this stamp is applied after such a gun has passed Belgian proof firing.  There's a lower case "e" on its back with a line to the right that's below the number "66" that's stamped on the upper left flat of the trigger guard.

This pistol also has some interesting characteristics which are typical of the earliest examples of Browning designed auto loaders.  The milled shape of the recoil spring housing on serial number 4 is similar to the shape on M1909 and 1910 Colt prototype automatic pistols and is also seen on serial number 6.  This differs from what was actually put into production (see serial number 469 below).

The number "4" is the same as the "4" as on serial number "469.

There's a lower case "e" on its back with a line to the right that's below the number "66" that's stamped on the upper left flat of the trigger guard.

Right side view - frame has the number "66148" stamped on the right forward portion of the frame.

Production examples of this model have a left pointing arrow at the end of the slide that points back to a takedown line.  Serial number 4 has this feature, but the arrow appears to have been an afterthought and was applied at a diagonal under the pin that holds the recoil spring plug.  In addition, there are two similar arrows stamped on the right side of the slide (pointing down) and on the right side of the frame (pointing up) that also align in order for the barrel to be twisted for removal of the slide.  For comparison, serial number 469 has a variation of this arrow horizontally from right to left above the pin for the recoil spring plug.

Close-up of take down marking on slide. (above and below)

Early style rear sight and plunge milled serrations.

Close-up of Belgian proof marks on the slide and frame.  These Belgian proofs are where British proof marks are typically located.

Left side view of the slide.

Left side slide markings from Colt Model 1903 Pocket Hammerless serial number 4 show that these markings were individually stamped.  Bill Goddard notes on one of the pilot series Colt 1900 pistols that the word "AUTOMATIC" was hand stamped, so this marking method was used on the earliest pistols.

For comparison, here is the left side slide marking from Colt Model 1903 Pocket Hammerless serial number 469.  These markings were applied with roll dies.

Right side slide markings from Colt Model 1903 Pocket Hammerless serial number 4 show that these markings were individually stamped.

For comparison, here is the right side slide marking from Colt Model 1903 Pocket Hammerless serial number 469.  These markings were applied with roll dies.

The Rampant Colt in a circle on serial number 4 was applied with a roll die.

View of inside of slide showing earliest style of milling.

Checkered walnut grips with uncheckered border.

Back sides of checkered walnut grips.

Type I 4" Barrel (with Belgian proof mark), recoil spring, recoil spring guide, barrel bushing, and Type I magazine (full blued, pinned base with high polished base plate.)

Recoil spring guide (front)

Recoil spring guide (rear)

Barrel bushing (front)

Barrel bushing (rear)

Barrel bushing (side)