Steel 1050 and Nebulous Gray 630 look pretty similar to me, at least in natural light. I gave my Steel 1050 WF a good vacuuming today and got this picture of it with my Nebulous Gray HLT:
One consideration is that this WF is 10 years old, and I don't know if the current Steel 1050 is going to be exactly the same as the Steel 1050 from 2010.
Edited: I just checked my order history, and the HLT above is 630 Recycled, not 525 Ballistic.