Oil cooler - but is it?

[02GF74]

I've seen a few of these on eBay, described as " Yamaha VMAX V Max Oil Cooler".
I am not aware of there being an oil cooler fitted plus there are no fins hence it looks to me like a reservoir, possibly fitting to the cylinder head?

Anyone know what it is? Pictures below.

underside - aha, I see rust so would imply water flow - is it an oil-to-water cooler?

 

[MaxMidnight]

It is the water/ oil device (a.k.a. known as the pencil box) that sit atop the crankcase between the barrels parts 50 to 52.

 

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https://www.vmaxforum.net/threads/how-to-overhaul-crankcase-breather-housing.17004/

 

[one2dmax]

PCV system and oil to water pre-heating. The manual may describe it's function in more detail.