The truth is that tin and iron toys are no longer mass marketed because plastic is far cheaper to make.
Metal does have edges, which, when left unfinished, can be sharp.
And all mechanical toys have small moving parts which can come loose. But plastic toys can break too, and they usually cannot be fixed. There is NO substitute for parental supervision, none. Don't feel bad if you have trouble telling them apart. I've seen replicas with large price tags in antique stores, so sometimes even those who should know are fooled.