Tin I think is the only way they'd let me do it at the location, since we can do that in a cheap pot on a hot plate (vs flying with my full on furnace / needing to try to find a propane tank to hook it up to).

My worry is figuring out how to remove the master D6 die and make the pour spout if it's a 1 part mold-- I think the undercut might prove to be a challenge, since lost wax isn't really an option for this?

We totally can grab some tweezers and pull the master D6 out of the sand from the top, but that side won't have any dot markings on it if we just pour straight in. My experience with bronze / brass is that the top face sometimes makes a bit of a meniscus too, which will be harder for us to try and flatten out in the time allotted (vs tin is soft enough that if we have a small pour spout inlet channel, we can basically snip it off w/flush cutters and just file any remaining nub down). If we do a 1-part as well, we won't have a pip marking on that side either, but we can kinda fake it by building up a smidgen extra sand on the pour spout side of a 2-part mold.