What is this part?

Hello, I've got a 6-71 detroit, 4 valve in a 42' Uniflite and I am in the process of replacing the head. I want to clean and paint the engine, but while doing so, I ran across this strange looking part. The service manual really doesn't describe it, or at least I couldn't find it in the 960 pages.
Does anyone know what this part is? It's bolted on to the lower front of the block and the base of the part seems to be made from aluminum, while the upper part looks like a tin can.
Please check out the photo and if you know what it is please enlighten me.
Thanks,
jim

That a crankcase breather

thanks marv.
I'll look it up in the service manual to see if I can find out how it works and what to do if it goes bad.

Hello and Grettings from Venezuela...

This Breather is a OLD and EARLY vertion of this system.. not all catalogs do explode that option

All new engines have the breather in the aluminum rocker cover,,,, (I do recomend to upgrade all engines to this vertion of cover, it is the solution to all the oil mess caused by oil filtration thru the Neoprene gasket of the Steel Stamped cover....)

The aluminum cover also make the engines look much better.....

Regards