Ola
I am no expert however if i remember correctly from my marching band days,as a rule of thumb a B flat has 3 valves and 90% of them are brass.Most G sharp trumpets were 2 valve and were mostly chrome.
I am sure there are some exceptions to all of what i have suggested but i would say it is B flat as you have the mutes(not many people would use a mute on a G as they were better for power and the top end of the scale)
I will stop now as i am boring myself!!!!!
Hope that helps