Hello, it should be lamb, beef is a little darker than this, and the fiber is thicker, you can chew a little, because just look at the picture is no way to judge, you can conclude from the taste and color and aroma. Lamb is more white and the meat is looser, beef is very firm and has thicker fibers.

Personally, I think it should be lamb. Lamb is also sinewy, near the bones are sinewy.

Hope it works for you, hope to adopt~