NB - 'chuck':  Your, 1897 dated, Steyr  Krag was built in Austria and started life as a Model 1894 Norwegian Army rifle (in 6.5 X 55mm).  Norway contracted with Steyr to build some rifles during 1896 and 1897.  The 1897 serial numbers ranged from 30,001 to 39,000.  Your bolt may have been replaced, but, the "8 & 762" numbers appear to match the last four digits of your receiver's number, 38,762.  Some 'Steyr-Krags' found their way to South Afrika, during the Boer War.  These are quite rare and IIRC, not in your serial number range.
  It is likely your Krag was rechambered in North America for the 6.5 X 54mm Mannicher-Schoenauer cartridge, after WW2.  In the 1950s, Dominion (Canadian Industries Ltd.) 6.5mm M-S ammo was easier to get than 6.5mm 'Swede' or Italian-Carcano.
  The chamber-alteration was either done by shortening the dismounted, left-hand threaded, barrel at the breech end and re-chambering or by inserting a chamber 'liner'.
  As I advised in an earlier response, it would be a good idea to have this rifle checked by a knowledgeable 'gun person'.  (Attached photo of 'Boer' General Tobias Smuts with Model 1894 Steyr made Krag).
  Photos of your rifle would be enjoyed by all and may beget more information.

Also, I measured the chamber with a 1/4" wooden dowl, and it measured exactly 52mm. A 54mm cartridge would be too long.

NB 'chuck':  Your Steyr Krag is in the serial number range of the Norwegian Model 1894 Infantry rifles built in 1897, (#30,001 to #39,000).
  I said, it is not in the range of Boer (OVS - Orange Free State and ZAR - South Africa Republic) Steyr Krags, that seem to number below #900 and lack some of the Norwegian markings.

Clear pictures of the numbers and markings on your bolt would be interesting.
  It appears your barrel has the small 'swastika' marking of a Norwegian steel or barrel producer.  This marking is common on early Norwegian Krag barrels and has nothing to do with the Nazis.
  There are a couple of filled screw-holes in the groove on the left side of your receiver.  It appears a scope was once mounted on this 'sporterized' Krag.

NB'chuck':  The 6.5mm M-S and 6.5mm Carcano are very similar cartridges.  I have heard of a number of Norwegian Krags altered to the once popular and available M-S round.  Back in the 1950s, 6.5 Carcano was rare in hunting loads.  In fact, M-S brass was used to make reloadable Carcano ammo.  The Carcano round is just an unlikely candidate for re-chambering.

You may have to resort to having a chamber cast done to accurately measure your chamber.  (I no longer have any 6.5mm M-S brass laying around.  Otherwise, I would send you some cases to play with).

Here are some dimensions from one reference:

I made a plug out of a pencil and closed the bolt on it. It measured 55 mm. A 6.5x55 cartridge wont go in all the way so I marked the cartridge at the edge of the chamber and it looks like the same measurement as the6.5x54 M-S. Is it possible to be any other than this cartridge?

Bottom of extractor