Green’s Dictionary of Slang

1. a smile.

1893		Illus. Sporting and Dramatic News 11 Mar. 28/2: I [...] tried to beam on a friend – albeit, a poor beamer at the best [OED].
2001		K. Sampson Outlaws (ms.) 6: Smiles all round. Grins for Uncle Ged. [...] I locks up [...] giving the boys a nice big beamer back to let them know we’re rocking again.

2. a blush.

1998		I. Welsh Filth 28: The constables get big red beamer up the side of their faces.
2000		N. Griffiths Grits 74: Phil sits back with a beamer, all fuckin sulky like.
2012		(con. 1980s) I. Welsh Skagboys 254: The wee lassies looking coy, the wee laddies gittin beamers.