What it is:
A US Ordnance Corps button ...which actually is not an Artillery button. The US Ordnance Corps was a separate and distinct branch of service from the Artillery Corps. (For example, it was in charge of issuing weapons and ammo, including bullets as well as cannon projectiles.)
This button is listed in the Albert button-book as OC3.
Well worth noting is that this one is MUCH rarer ...because it is gilted. The great majority of this pattern never had any gold on them.
What time-period it's from:
Depends on the backmark. If this particular pattern of Ordnance Corps button has "Robinson, Jones, and Co / Makers / Attleborough Mass" on the back, it was made between 1832 and November 1834.
If the backmark is "Wadhams, Webster & Co / Superfine / Wolcottville Conn" it was made between 1838 and 1846.
"Scovills / Waterbury" on this button means anytime between 1840 and 1851, when the Ordnance Corps' emblem was changed (shown in Albert as OC5).
An OC3 button backmark saying simply " * US * / Ordnance Corps" is 1830s. The McGuinn-&-Bazelon backmark book notes it was probably made by Scovill.
Regards,
TheCannonballGuy (PCgeorge)