From a friends information;
What really happened:

Remington was directed to divert 20,000 receivers from its 03-A3 production for A4 production.

All A4's were built from the ground up in a separate area of the Ilion plant. The notion that A3's rifles were converted is untrue.

The second order for 8,365 was issued on 20 june 43 while the first batch of 20,000 was still in production. The serial number range assigned for the second batch was 4,000,001 to 4,015,000. This range was large enough to handle the second order plus reconcile any scrapped receivers from both orders.

Production of the second A4 order's receivers commenced in Sept or Oct.

Meanwhile A3 production was going great guns. Remington was shipping about 60,000 A3 rifles a month and in the process overran the A3 serial numbers into the range assigned to the second batch of A4's.

By the time anyone noticed about 3000 A4 receivers had been made using serial numbers already used on A3's.
The decision was made to add a leading "Z" to the serial numbers of the A4's in the range 4,000,001 to 4,002,980 (~).
NB: Virtually all "Z" series A4's have Sept 43 barrels.

Receiver markings were never changed to "03-A4". Some A4 rifles markings apparently were so altered years later during rebuilds possibly after the A3 was obsolete.

After the numbering mixup ordnance assigned a new range of serial numbers to Remington beginning at 4992001 which was to be used for the balance of the second A4 order, a proposed but aborted third A4 order and finally the remainder of any A3 production. As it happened A3 production was suspended in Feb 44 and A4 production finished up that summer when the last few rifles finally got telescopic sights.
NB: virtually all 499nnnn series A4's have Dec or Jan 43 barrels.

The total number of A4's shipped was 28,365.

Each of the major references like this website cite a different upper limit for the last A4 made. The variance is as much as 2000 rifles!

The best information available to date was prepared by Bill Hansen in his article for the Remington Society of America Fall 2004 Journal on A4 production. Mr. Hansen reconciled the actual shipping data with estimated scrap rates to come up with calculated month by month production. His upper limit is within a couple of dozen rifles of the highest number rifle that i know to exist. A table of his A4 information is in a sticky on the milsurps forum and his information is also credited on vishooters website, another very reliable source.

early M1903 striker rod..looks like phosphate, should be black oxide..cocking knob too early..is the bolt marked R?

From the expert...John Beard about your rifle;

The “Z” prefix means the rifle has a duplicate serial number. In this particular case, the duplicate serial number appears on another Remington ’03-A3, NOT an ’03-A4.



The rifle appears completely original, and in pristine condition, except that someone replaced the firing pin assembly with something from an M1922.



Hope this helps.

I answered your question one minute later!
You need a mid 1943 correct bolt assembly and striker rod..otherwise just as it left OG after inspection, probably just after WW2...yours is from an SA M1922..incorrect for your M1903-A3.

According to John, as your striker rod looks funny, it is from a .22 caliber SA M1922 rifle. The bolt body is from a Remington rifle.
It can be restored to an "original" M1903-A3, with a correct bolt..They usually sell for $75.00-$150.00...its so sad an original bolt is not with it. Id get a complete RA bolt from the same era your rifle was made..it should be original. However, the Ogden OG does detract a bit..not much considering its so nice otherwise.
Perhaps the original owner has the correct parts?
I dont know how it works, but myself..I couldnt sleep knowing the bolt wasnt original..I bet you can find the right bolt from Bill Ricca, or ask on the Jouster CSP boards..Lots of '03-A3 guys there..

Doctor Bill...please e-mail me at waffenamt@aol.com

From CSP

"The firing pin is a commercial item, built for or by Numrich. It was coupled with a modified M2 22 cocking piece, an M2 firing pin nut and an extra strong spring to make a short fall, fast lock time conversion for the M1903/03A3. I bought one and still have it . For slow fire it was O K when used with a commercial trigger, but not so good with the standard 03/A3 trigger. For rapid fire, the heavy spring made the cocking of the FP motion hard. There is no resistance for about half the bolt lift, then it becomes difficult. It is sort of like the 03 Garand FP set up."