Winchester used the No.2-1/2 and No.2-1/2 W on occasion for factory loaded metallic shot shells. And that they also used the No.2-1/2 W primer in shot shells when loading a "Top Load" for Proof Loads for firing at the factory and I believe those were Paper Shot Shells not Brass. Also, That may have only been used for a brief period in 1914.  

The No. 2 Improved Winchester primer (plain copper) is proper for all Black Powder shells after 1884. The No. 3W Winchester primer (copper with W marking) and the No. 2 1/2 W Winchester primer, bras with a W in a circle is proper for any Factory loaded shell primer to 1920. After this time, the No. 3W Winchester copper primer is listed as the proper load until 1934. In 1934 the catalog listings indicate both the No.3W and the No.17NF (NF = non-fulminate) are proper. The No. 17NF at that timeframe used a plain brass cup. During WW1 and into the early 1920s, some shells will rarely show a brass primer marked with W. This indicates a NF priming formula being used in a No. 2 1/2 W primer. 

If you de-prime the shell and separate the anvil from the cup, I likely can tell you would type of primer it was. Is the primer copper or brass? Its most likely a Winchester No. 2 Improved Primer be my initial guess.

Based on its fired condition and the remains of the crimp used on the end of the shell, it was most likely came from Winchester as a NPE (New Primed Empty) shell sold for loading / reloading on your own and intended for loading with Black Powder. 

There are a lot of Cowboy Action Shooting guys that reload these old brass shells with Black Powder. For a crimp they simply superglue the top card in place instead of the traditional rolled crimp. But like you said, probably best to purchase a modern brass shell or plastic shell for loading to shoot.

Sincerely,

Maverick

P.S. All that primer information comes from information provided to me by Dan Shuey and is also mentioned in several of his books.

30gov03 said

Bert H. said
 I believe that the "No. 2" stamped on the base of the shell indicates the Winchester No. 2 primer.
Bert
  

Take a closer look. The shell is marked "No. 12", identifying the shell as 12 gauge. This was fairly standard across the major ammunition manufacturers in the late 19th and early 20th century.
FWIW, Winchester's all-brass shotshells were primed with their No.2 (for black powder) or No.2-1/2 W (for smokeless powder), identical in size to our modern "Large Rifle" primer.
Jim
  

Cool! I feel these should not be reloaded but they make great eye candy. If they were ever fired with Holy Black or corrosive primers and not properly cleaned their integrity will be compromised. There are modern versions that are safe to load and fire even if they don't have the historic appeal of the ones in the OP. 

Mike

30gov03 said

Bert H. said
 I believe that the "No. 2" stamped on the base of the shell indicates the Winchester No. 2 primer.
Bert
  

Take a closer look. The shell is marked "No. 12", identifying the shell as 12 gauge. This was fairly standard across the major ammunition manufacturers in the late 19th and early 20th century.
FWIW, Winchester's all-brass shotshells were primed with their No.2 (for black powder) or No.2-1/2 W (for smokeless powder), identical in size to our modern "Large Rifle" primer.
Jim
  

Good catch, and thanks for the added information.

Bert

Bert H. said

 I believe that the "No. 2" stamped on the base of the shell indicates the Winchester No. 2 primer.
Bert
  

Take a closer look. The shell is marked "No. 12", identifying the shell as 12 gauge. This was fairly standard across the major ammunition manufacturers in the late 19th and early 20th century.

FWIW, Winchester's all-brass shotshells were primed with their No.2 (for black powder) or No.2-1/2 W (for smokeless powder), identical in size to our modern "Large Rifle" primer.

Jim

First comment... I would not try to reload those old shell cases. 

I believe that the "No. 2" stamped on the base of the shell indicates the Winchester No. 2 primer.

Bert

Maverick said
It all depends on how vintage they are / when they were made. If there very old they used the Winchester #2 Primer.
Pictures would be most helpful?
  

True, but I suspect that they are WWII or later vintage, and if that is a good assumption, a 209 primer would be appropriate.

Bert

Pictures would be most helpful?

Spud said
That's a real nice buck Mark & taken with a nice rifle/cartridge combo. A great shot too with open sights!! I still use my Win 95 carbine (also in .303 Brit) when chasing deer here in Oz.
Spud
 
  

Spud,

That's a fantastic picture!  Thanks for posting it. The part of the state where I hunt is known locally as the Oregon Outback because much of it is looks very similar to your Australian Outback.

After being an avid hunter in my youth, I have to admit that hunting had become kind of mundane over the years and had become more of an annual routine simply to put venison in the freezer.  Several years ago, I started hunting with older firearms and open sights and it has rekindled my interest and enthusiasm for hunting.  It's much more of a challenge and far more rewarding than just harvesting venison.  Thanks for watching the video.  Mark

Spud

While I am not 100% sure, I believe that the No. 209 primer is what you want.

Bert

Congratulations, and thanks for sharing!

Tony