Petcock Orientation for Main vs Reserve

Hey all,
The new-to-me 1978 KZ650B petcock has large end and a small end. The large end has the bumps (see photo) The seller wasn't sure which end up would.be main vs reserve. Can anyone help me out?
Thank you.in advance.

I can’t see your photos but if you look really close there may be an arrow on the lever. It’s small.

Hey Blipco,
Thank you for replying.  I don't know why the photos weren't there to begin with, but i just uploaded two different shots (my apologies for the multiple uploads of the same shots).
I don't see any arrows. I see 1-2 Ebay sellers with the exact same unit, but no word on which way is main vs reserve.  I've sent an Ebay communication to one of the sellers (they appear to be the same person with 2 stores), and I'm waiting on a reply.

You don't have the petcock off of the bike, I don't guess? It would be a simple task to blow down the taller pick-up tube & see which direction the handle needs to be in. 

If I were to guess, judging by the symbols, I’d say you were in reserve now.
If you pull the fuel hose off, you could drain the tank in one position then turn the knob and see if any more comes out.

 

All bets are off. That's not a stock Z650b1 fuel tap. 

I don't believe it is stock, as the lack of symbols is something that UJM's for sale in USA in 1978 should not be lacking.  But, I see photos online that purport these to be stock... just maybe not in USA. I'm not worried about stock or not.  The owners manual shows the kind of lever that has one long side and english writing, not two sides with one side having the ridges/bumps with no writing.

Also, if it were off, then this would be a simple exercise.  If I wanted to risk it, I could just ride it until empty and see if I had any reserve or not.  I have a quart rescue can of gas, so I guess that's my best option for the time being.

Thanks for the responses.

Barry

That's not stock in any market. I'm in the UK.