Tann ten Lever Locks 6.5 gauge

[Ant]

See these two locks I found the left hand lock case spare (LH pic) and as it occurred to me that it is handed the other way to the standard Right hand one (in picture).
As there was no bolt assembly or lock cap with it, I have made one up (just to see how difficult it would be) as no brass to hand used an old mounting block off a Tann anti Herding device just the right size, lenght and width only trouble is the bit missing from the bolt (where the fixing bolt went through) still can always braze a bit in there later.

So What I want to know is which way would the key hole be cut as for the life of me I can't ever remember seeing one handed this way Though I must have at some time But water under the bridge and all that, plus brain full up with other useless information.
Regards to all and seasons greetings Anthony.