J. Kissel

I took some pictures of the SPI pathfinder's (QTY 4) IXM100.C2-VC (right-handed) and (QTY 2) IXM100.C2L-VC (left-handed) mounts in their "raw" pre-assembled clean state since 
    (1) it's my first time dealing with Siskiyou mounts,
    (2) the "assembly procedure" D1100362-v1 thus far is only an exploded view of numbered-but-not-labeled and out-dated parts for am unspecified, but left-handed mount, 
    (3) they come out of the clean-and-back process quite disassembled but maybe in the same bag,
    (4) it's always useful to show what each company's convention of "right" vs. "left" handed optics mounts so you can tell them apart, when you've got lots of unlabeled clean mounts in front, and
    (5) "right" and "left" are perspective-dependent descriptions of convention, and so it's useful to unambiguously specify.

So -- to determine if they're right- or left- handed -- orient the optic holder with the optic (back) side towards you, and the adjustment knobs (back) side away from you. Rotate the mount such that the optic-securing #8-32 set screw hole is up. Hold up your trusty left-o-meter -- your left hand formed into a capital L shape with your index finger and and thumb (palm facing away from you). If it matches what you see, it's a left-handed IXM100.C2L mount with the "opening" to your upper right from the described perspective. If it doesn't match, it's an IXM100.C2 with the "opening" to your upper left from the described perspective.

First picture is both mounts side-by-side; four right-handed IXM100.C2's on the left and two IXM100.C2L's on the right.
The second-thru-fourth pictures are various views of the IXM100.C2 right-handed mount. In the second picture I'm making the American sign language letter R.
The fifth-thru-seventh pictures are various views of the IXM100.C2L left-handed mount. In the fifth picture I'm making the American sign language letter L.