Cuthbertson wrote "...On Service,
leather Hammer-stalls are undoubtedly an advantage to a Battalion, when loaded, and resting on their Arms, as accidents may be prevented by having them fixed upon the hammers of the Firelocks..."
(page 93, XIII of "System for the Complete Interior Management and Oeconomy of a Battalion of Infantry")
The following are orders for the Royal Artillery Regiment, issued at Philadelphia on 2 June 1778 in anticipation of the march to New York which culminated in the Battle of Monmouth. "It is left to their [officers] discretion in time of real Action to disencumber such men as they may think proper entirely of them [arms], taking care that they be lodged in their Ammunition Carriages and to prevent any possible Accident happening therefrom,
thumb stalls have been ordered to be provided which the men are constantly to keep on the hammer of their pieces except when posted centrys." Source: Great Britain, Royal Artillery Regiment Library, Woolwich, Brigade Orderly Book, James Pattison Papers.
(Note from Gus: Before my old computer crashed, I had a couple of quotes that reported hammer stalls to be on the locks for Sentries, until/unless they had to actually fire. Perhaps this is a case where there was enough "enemy" threat to justify taking off the hammer stalls?)
"On the morning of 21 December 1808 the 2/23rd Foot was approaching the village of Sahagun when firing was heard in front. Lieutenant Colonel Wyatt immediately gave the order,
'Off hammer caps' which, Thorpe recorded, 'caused a thrilling sensation of delight, expectation, and ten thousand other thoughts and feelings impossible to describe'. (11) This was followed by the command, 'Prime, and load!' and 'the ramrods rattled gaily in the barrels, bayonets were fixed, and as if their musical jingle had raised the spirits of all', the battalion moved forward at the 'double quick', eager to see action."
A fairly late reference in the 2nd (Queen's) Regt standing orders 1802 that may merely muddy the waters further.
"Serjeants, bands and drums, to be always provided with white leather swordknots and gloves;
the men with black leather cap for the hammer of the firelock."
Through quote from article by laurence Spring, pp31-2 First Empire Magazine 38
Some of the above information from:
http://2nd95thrifles.myfastforum.org/archive/hammer-caps-frizzen-covers__o_t__t_1092.html
Gus