LF: R5159 - what is it?

["John RABSON" <john.rabson@numeo.fr>]

I have been given a box labelled "FET" which contains assorted semiconductors 
and which was part of the estate of a deceased amateur.

In it there are several stud-mounted devices labelled R5159 with what appears 
to be a date code of 505.  There are three wires sticking out of the top and 
the package looks good enough for several amps.  The manufacturer's logo is 
rather smudged and looks like a cross between a heron in silhouette and the TI 
symbol.

Can anyone identify them please?

73
F5VLF