These cheapie Evemodel N scale freight cars first started appearing circa 2020 and, at least as of this 2023 writing, not much is known about them (apart from speculation that the models are probably knock-offs of cars sold by one of the major mfr's).
Refrigerator cars as a whole gained acceptance in the mid to late 1800s (1880 +/-). All of these early cars were made of wood. Metal frames became common with wood bodies in the early 1900s and this general practice would remain until the 1930s when the first major production of all-steel cars began. Many wooden cars were updated with steel ends and roofs starting in the 1930s until the cars were being retired in the 50s and 60s. Although Evemodel doesn't provide any information on the prototype for this model (if there is one), it appears to depict a car that has been upgraded with a steel roof and ends.