Adrian, glad someone has something to ask at last !
 
Follows some lecture notes relative to caps that I gave at the NAM about six years ago.
 
PERCUSSION CAPS      SLIDE  27
Large quantities of caps are found and many of these are in a very good condition although the fulminate will have long ceased to be present.   In general, the British caps are distinguished by having four flanges and the Russian and French have six.   The British, alone, are for the most part stamped on the crown of the caps with government marks.    The cap composition was a mixture of fulminate of mercury with potassium chlorate and powdered glass.
All the British ones that are marked in the crown bear a Broad Arrow with additional marks as listed :�
1.      SLIDE  28      Broad Arrow without anything else.
2.      SLIDE  29      ï¿½B O�  representing The Board of Ordnance.
3.      SLIDE  30      ï¿½W�        the mark of the contractor, S. Walker & Co., Legge Street, Birmingham.  Percussion Cap  Maker.
4.      SLIDE  31      ï¿½J�      the mark of Frederick Joyce,  57 Upper Thames Street, London.  Percussion Cap and Wadding Manufacturer (also made cartridges from 1852)
5.            SLIDE  32      ï¿½A�    Made with � Sulphuret of Antimony� now know known as antimony sulphide.  Gives a longer flash with less violence than fulminate of mercury.  This was mixed with potassium chlorate.   This special composition was first ordered by Lovell in 1835.   In the 1860s caps containing a similar composition are crown stamped with A and the date, e.g. A / 64
A small number of  four flange caps with no markings are noted.  These are slightly larger than the government caps and the origin is unknown.   They are probably British.
SLIDE  33      The six flange French and the Russian caps are unmarked but the Russian caps when found in good condition are noted as having a paper covering glued over the open end of the cap.
===================
 
Later notes - not all the British caps are marked and I have an small original 1856 brown paper paper wrapper from a larger cap pack stamped for 1856 containing 15 unmarked caps,
 
A couple of rarities have shown up out in the Crimea.  These appear to be British but the crowns are impressed with the Sardinian cross.  I believe these to be British made for the Piedmont Sardinian units although the Sardinians own caps were of the French pattern.  No documentary proof of my assumption unfortunately.
 
One of the things I noticed was that no caps were found marked for Eley Brothers and I am assuming that these may well have been the unmarked ones ?
 
Your thoughts ?
 
Bill

Adrian
 
Your WR&Co caps are those specially made for the WR capping BL carbines and rifles. They are somewhat stronger than normal to aid the burning through of the cartridge wall.  I have a bag of those somewhere.
 
The caps are broad arrow marked as I indicated.
 
My cap photos are all pre-digital.  I will try and make a fresh set in digital form - watch this space !
 
Bill

Hi Bill, wow, excellent picture! Thanks very much for sharing that with us. The stamped marks are remarkably clear on these examples. On the weekend I'll try the same with the caps I have. Have you found any one particular type has dominated the findings? Adrian

This is the selection that I was fortunate to obtain. The date markings from "6" to "64" in particular are very faint, in fact these samples, as faint as they are compared to the earlier & later types, are among the best of the batch. There are hundreds of the "63" �stamped caps & most are extremely faint, many dates being difficult to discern without a looking glass & good light. (my wife is used to me doing such bizarre things as spend an entire afternoon inspecting & sorting approx 1500 percussion caps, whooping with excitement every now & then as a "new" type is found!)
 
I am not entirely convinced about the caps marked "6" & "61", �perhaps they represent 1860 & 1861. But given that so many were poorly marked �they leave me uncertain - though there are a few of each & so are not isolated examples. I hope to find some similar examples from another batch to be reassured that they are not mis-strikes.  
Do you know of any examples which post date the Crimean conflict?
 

 
 
The unmarked cap is similar to the plain 4 flange cap in your picture. It is interesting to see how the stamp has been from the "inside" up to 1864 & from the "outside" from "A 64" onwards.  
Adrian.

I do not think that they have been cleaned. The Crimean soil seems to be remarkably acid free and even the iron cups in the bases of the Mini� bullets have very little corrosion.  The Russian caps have paper pasted over the open end and even this survives to some extent.  I 'cooked off' a couple of the British caps and obtained small exothermic reactions from the traces of composition, and this after 150 years in the soil.