What is this old "lemon-squeezer" shaped pan We found this odd pan at  the family's summer cottage. The cottage is in Central Finland, and used to be a croft before my grandfather bought it. This thing has been on the edge of the stove for a while, and nobody seems to know what it is.

By the way the handle is pointing, the pan is supposed to be used convex side up. The convexity is about ten centimeters high, and has chevron-shaped ridges forming channels down the mound. It looks a bit like a lemon-squeezer from the side, but with a shallower slope. There's also a channel around the base of the mound, and a beak for pouring. The pan is about the size of my outstretched fingers, or a small frying pan. Here's a side view:



I tried a reverse image search and came up empty. The one guess anyone made is that it's a pan for melting fat, but I couldn't find an image of one of those on Google.
What you have appears to be a vintage or possibly antique cast iron grill pan.

The pan would be used on the stovetop and could be used for steaks, chops, burgers, bacon, certain vegetables, etc. The ridges can provide grill marks, and the channels allow grease to drain away. The shape allows the grease to drain to the outside channel where the pour spout will allow the grease to be poured out of the pan.

As with the grill pans of today, the pan would be pre-heated and the meats or veggies would be cooked at a medium high or high heat, much like outdoor grilling in the US. Also, it would be good for camp-type cooking over an open flame.

Re rendering fat, I suppose it could work but with a low or slow heat. 

Update: As per @Sneftel's comment, these grills can have many different uses. @Falken's answer addresses one of these, but certainly not all. In addition to the uses mentioned previously, see this snippet from WebstaurantStore:


  An all-around convenient stovetop grilling solution, this 10 1/4" round heavy-duty cast iron barbecue plate is perfect for making a variety of delicious items including Korean barbecue, pita bread, naan, grilled tortillas, and roasted vegetables.


Similar pans can easily be found online by searching for Mongolian bbq grills.