Any idea why Spam uses such unusual cans?
Tradition!
All I know is the can is molded around the meat and sealed with the meat inside already so it’s probably easier to just give it a peel open top. I don’t know. The answer to your question most likely lies within the Spam Museum and as god is my witness I swore never to go there again.
[quote=“Inner_Stickler, post:3, topic:694408”]
All I know is the can is molded around the meat and sealed with the meat inside already …/QUOTE]
That sounds really weird. Are you actually saying that the can is wrapped around a block of already-formed meat product?
Surely the uncooked meat paste is just extruded /squirted into the cans before capping, sealing and pressure cooking?
What you describe is what I was meant but not apparently what I said.
I thought you were describing a conveyor belt of meat blocks being wrapped in metal.
The rectangular design of spam and other meat cans makes them pack better for shipping - I guess the real question is why tomatoes and beans etc aren’t also in squarish cans.
Reported
My guess: A rectangular hunk of “meat” is less likely to roll off of your cutting board than a perfectly cylindrical one. Foods that form piles (e.g. canned corn/beans) don’t have this concern, so a round can is perfectly fine for them.
Additional: A rectangular can makes it easier to bow the sides of the can out and get air in behind the Spam block, allowing you to slide it out of the can without destroying it. I face a similar challenge every Thanksgiving when I try to extract a perfect cylinder of cranberry jelly from its can in a single piece; I end up using a knife to jab a couple of airholes in the bottom of the can to relieve the vacuum and allow the stuff to glide out without a struggle.
Maybe the consumer was thought more likely to prefer that the produce comes out square, for serving or slicing, and it is problematic to open a square can with a conventional can opener.
the same reason tuna cans are like they are; to be repurposed for hobby and storage purposes. if the can is a unique shape then you will buy more of them.
Does the can still come with a “key” for self-opening?
The ones I’ve seen lately are pull-tab fully-removing lids, like soup or canned cat food lids.
ETA: like this. (No, that’s not a SPAM can, but an example of the kind of can I’m describing.)
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We think it’s unusual as Spam is one of the last products to come like this, but many meat products had weird cans in the older days.
Sardines and such are typically packed in similar, though much shorter, cans.
Canned corned beef of at least one major brand seems to commonly be packed in tallish, rounded-rectangular, tapered aluminum cans. I have no good explanation for that.
Others seem to use the same kind of can as discussed here for SPAM.
My guess is that’s it’s designed to be opened on the large end, and when it’s then placed large-open-end-down on a plate, the taper makes it easy for the meat to pop out all in one piece.
Many, many brands. Most.
You jab holes in the bottom of a can with a knife? Wouldn’t it be so much easier and more effective to use a church key? (You could even get religion and get your soul saved at the same time! 
)
(Church key photo from this Mental Floss page: 11 “Modern Antiques” Today’s Kids Have Probably Never Seen.)
An even better strategy for removing canned dog food, that should work every bit as well for canned cranberry: Open the can at both ends. Remove one end. Leave the other (now severed) end in place, and push it into the can, thus extruding the cranberry from the other end, like a piston in a cylinder.
HTH.
These techniques work fine with cans that have lip on both top and bottom. Many modern food cans, however, only have a lip at the top. The bottom is rounded to allow cans to nestle a bit when stacked. Getting some kind of opening in the bottom can only be done by poking a hole. An awl or ice pick is probably the best tool, but a knife properly wielded will work.
I suspect that the spam can was based on engineering/business criteria such as, “We already have a machine to do that,” or “it’s easier to retool the machines to make a square can than to switch to round cans.” Maybe a key-opened can was just de rigeur for Hormel, as evidenced by all the other meat products that used it like canned hams .