Ortofon SMG 212 Question

Hello A-goners! I have a quick question for all the Ortofon SMG212 owners out there.

I just bought my first Ortofon SMG 212. It's in great shape, but it didn't come with a headshell. I plugged my Yamamoto headshell into it and there's a bit of a gap between the tip of the tonearm collar and the heashell. It's just a hair shy of one millimeter to be exact. Same thing with a vintage SME headshell that I have.

Any thoughts? The owner swears that it's all original and he has photos of an SPU G headshell that fit it with no gap (I couldn't talk him out of the headshell). I read that the SMG212 is supposed to compatible with SME style headshells, but it doesn't seem to be a "perfect" with modern universal SME style heads.

The one thing that occurs to me is that the gap looks like the perfect space for some kind of gasket. I seem to remember seeing washers or gaskets with some tonearms. Is this the case here?

Thanks in advance for any info you can offer!

P.S. Here's a link to a photo:
I would think that if the head shell locks into place with the tone arm, you should be fine. You could check out the plumbing aisles at Lowes or Home Depot and pick up the appropriate size o ring to fill in the gap.