Kelly-  Let’s see if we can figure this out for you, since there is some contradictory information provided.
609mm equals about 24 inches so we know the length of the barrel, which would be right for a M1 Garand.  The serial number CK9606 or SK9606 is totally wrong for a U.S. M1 rifle.  Russia in tiny print on the barrel would be an “import mark” required by federal law identifying the country of origin, so it is more likely a Russian made rifle.  However, the Russian Mosin Nagant rifles had either 29 inch (730mm) long barrels on the rifle model and 20.2 inch barrels (514mm) for the carbines.  The Mosin Nagants were made for 7.62 x 54mm Rimmed ammunition, which is a .30 caliber bullet, but the cartridges are not identical to those of the M1 rifle.  If your rifle is bolt action and the other long number by the Russia marking is 7.62 x 54 then it is a Mosin Nagant, oossibly with the barrel cut down to 24 inches.
The C/S9606 marking sounds confusing, but is actually pretty simple.  Federal law requires the serial number to be marked on the gun, and when imported, the importer translated the number from the Russian Cyrillic alphabet which uses the “C” but in English is actually an “S”.  This way everyone gets to same serial number in their record books instead of some people using C and others S.  This confirms it is a Russian made gun,
The Russian made SCT-40 Tokarev rifle is a semi-automatic, roughly comparable to the U.S. M1 Garand, but a heavy, long awkward gun.  The Tokarev does have a 24 inch barrel, so I am guessing that is what you have.  These were used during WW2, and after being replaced by the world’s most popular assault rifle, the Avtomat Kalishnikov 1947 (AK-47) the Tokarevs were sold off in the surplus market circa 1960-1990s.  While pretty cheap initially, the surplus dealer inventory is pretty much gone, and on the collector market the SVT-40 Tokarev rifles are running around $1,000 depending on condition and any special features.  Hope that helps.  John Spangler

http://pdf.textfiles.com/manuals/FIREARMS/jchiggins_88.pdf.

Hope this helps, Marc.

Peggy, our main focus at FineOldGuns.com (OldGuns.net) is military firearms. We sometimes list sporting shotguns for sale in our catalogs but we do not have a lot of interest in collecting them and are by no means experts in this field. A quick Google search on Progress shotguns led me to the following information at this links:

https://www.migunowners.org/forum/showthread.php?92103-Double-Barrel-Shotgun-that-has-quot-Progress-quot-stamped-onto-the-side

http://www.heirloomarmes.com/chapuis_pop.htm

PROGRESS SIDE-BY-SIDE SHOTGUNS
Just like their express rifle counterparts, the Progress shotguns are built on the Chapuis Armes double under lug locking system. This gives them a very sleek shape and exceptional strength. The incredible balance and light weight of these all steel shotguns make them very fast handling and a joy to carry.

Stocks are sculpted from Circassian or French walnut in either traditional English straight grip or pistol grip, with a semi-beaver tail forend. Barrel lengths include 24”, 26”, and 28”. Barrels can be bored, polished, and internally shaped for steel shot on request. Barrels are choked per customer request and fitted with ejectors and full length ribs unless otherwise requested. Sling swivels available at no charge on request. Calibers include : 12 ga. 2 ¾”, 12 ga. 3” 16 ga. 2 ¾”, and 20 ga. 3”.

PROGRESS CLASIC
Chrome bores, Coin finish on the receiver, Ejectors, English scroll engraving, Double triggers, Hand checkering, Dimensions on stock per customer request, Shipped in a molded case.

RGP MODEL - Box lock model with AAA walnut and plastic butt plate

Cal. / Retail
12 and 16- 2 ¾” / $2600
Cal. 12- 3” / $2700
20- 3” / $2900

RP MODEL - Box lock with side plates, AAAA walnut, Rosewood butt plate

Cal. / Retail
12 and 16 - 2 ¾” / $3600
12 - 3” / $3700
20 - 3” / $3900

RGP ARTISAN
Sculptured box lock receiver, Full coverage medium relief hand engraving, Floral décor and game scenes, AAAAA Fancy walnut, Shipped in a trunk type fabric covered case.

Cal. / Retail
12 and 16 - 2 ¾ / $5800
12 - 3” / $5900
20 - 3” / $6200

RP ARTISAN
Same as above except: Box lock with side plates, Floral décor with “al bulino” game scenes.
Cal. / Retail
12 and 16 - 2 ¾” / $7000
12 - 3” / $7100
20 - 3” / $7500

PROGRESS CUSTOM SHOP MODELS
Hand sculpted receiver, Coin finish, Exhibition Grade Walnut, Rosewood butt plate, Medium relief engraving with “al bulino” game scenes, Fitted linen and leather trunk case.

LUXUS
Sculpted Box Lock
All Cal. Retail-$9500

ROYAL
Model with Side Plates
All Cal. Retail- $13000

OPTIONS
Special stock designs and wood upgrades
Splinter forend
Extra barrels- Rifle and smoothbore
Special bore finish for steel shot
Custom engraving patterns
Single non-selective trigger

If this is the type of shotgun that you have, you are in luck but if your luck is like mine, it is more likely that your shotgun is one of a huge number made in the late 19th and early 20th centuries and sold through various retail outlets. This type of firearm falls into the category of "old guns" that no one seems to be interested in as shooters, but collectors do not want them either. Generally these were basic inexpensive simple guns which sold at modest prices and still have little interest or value on market today. On the retail market they usually sell in the $25-125 range depending on condition and general appearance for use as a "wall hanger" over a fireplace. Where there is any family history, we encourage people to keep these old guns for sentimental value. Please be warned that most of these are not considered safe to shoot.

Good luck, I hope that it turns out that you have a real treasure. Marc