Need help identifing the power rating for this resistor
I cannot say for sure who the manufacturer of this part is. I've used many of these sorts of resistors in my career, so my speculation below is made with a fair degree of confidence.

Renfrew wire-wound resistors that are 8" long and 1 1/8" in diameter are rated at 160W, which correlates with the 160D marking on the part. I'd hazard to guess that it's rated 160W (or very close to that). 

R5 on these sorts of parts usually implies 0.5 ohms. The other marks are probably tolerance and packaging codes. If you measure higher, and your meter is OK, the resistor may be somwhat fried.