Rutaceae

Citrus, spp., Unidentified giant lemon variety

This is a large Citrus species. The fruit were given to me years ago when I lived in Panama City's Old Quarter. Almost everyday I would visit a fruit vendor in Santa Ana to buy a small watermelon and a pineapple. He knew I worked with plants and collected fruit species so occasionally we would exchange fruit. I would bring miracle fruit, jaboticaba, jackfruit, curry tree fruit, and others, none of which he had ever seen. Him and his family would bring me highly regarded or lesser known fruit varieties from the interior of the country, giant Nance, Algarrobo (Hymenia coubaril), Mangos.

I never verified the species of this particular Citrus, it looks like some kind of Pomelo / Citron hybrid and has a relatively think skin compared to the size of the fruit. 

Any thoughts on the species?