Cu plumbing valves - what's this mess?

House from the 50's.
Not much of a plumber but just looking, seems a lot of hacking over time.
What is item B? What's it for if name is not self descriptive? Nut on side - a drain? Nut on top?
http://oi52.tinypic.com/deuult.jpg
Pipe to left of B is cold water coming in, hence the arrow marking.
D goes to a toilet
C goes no place. It's capped off out of pic.
A is a Beacon Mixing Valve 69. There's an adjustment screw on the other side. Web says:     "To operate: by turning the adjusting knob to the right (clockwise)      you can increase the water temperature; to lower the water      temperature, turn the knob to the left (counterclockwise)"
Don't know what there is a mixing valve there for. It's all cold water. Guessing it had a former use.
Unless B has a current function I'm guessing the whole mess from B to right could be removed and 1/2" Cu direct to toilet????
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

RG-
As mentioned, it WAS a mixing situation to provide warm water so the tank won't sweat.
Now it's all cold.....if you don't get sweating & don't envision reintroducing hot water, emove ALL of the valving and just plumb the toilet with cold water (which is what you have with the hot feed no longer active)
cheers Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.