I bought this excellent MK3 fat font insert from @Autaviano about this time last year for use with a late 1960s 5513 I had from that time. That watch is gone, and so this insert needs to go too! This one has a very nice thick font and also near kissing 40 which is a nice touch. Condition is really excellent with tiny little hairlines I've tried to accentuate with the photos. You can click on the photos to see full resolutions images. I bought it for 2200 USD last year, and selling it for the same. These were taken in lower lighting but are also useful for seeing the condition:
Here's a photo in more even and brighter lighting. Please don't hesitate to ask for more photos or angles if you want them.