Trigger guards can cause fits ,yes them kind of fits too.
A maker could cast their own ,or modify common ones to add their flair ,or touch.
Schools ( styles) of building had certain geographic influence on the shape of the tails on a guard for example and a region can at times be identified from such styles.
Your guard hints of a Pa. Type build ,but there were multiple builders in Pa. And ..Pa.type/style rifles/ guns built elsewhere.
Your guard shows a lug sticking up towards the wood stock. It should have a hole through it for attachment.
A finishing nail sized hole was common on rifles in the sixteen and seventeen hundreds and later depending on builder. A bigger hole might suggest another type arm.
If not for the width of trigger guard ,a more modern half stock rifle would come to mind.
Till some one recognises it ,Track of the wolf ,or Dixie gun works sell a lot of different styles you could browse for ideas of type arm ,and era.
It is quite small to be a rifle, yet the tang on the back looks long for a pistol. It doesn't appear to have ever been used, may have been a bad casting and discarded.