I'm pretty familiar with firearms in general, I've been shooting rifle and pistol for about 12 years now, but only recently acquired a shotgun, a Mossberg 590.   Where the hell are the markings indicating what size chamber this thing has?  The reciever  has "Mossberg 590" and "S#" on it but no chambering info.  Is it hidden underneath the heat shield on the barrel somewhere?  I just thought of this, but my shotgun is safely at home on solid ground about 1000 miles away.  

Thanks.
That's what I figured.  Kinda too late to be worrying 'bout it though, considering I already put about 40 rds of 2-3/4" 00 and 5 rds of 3" mag slugs through it last weekend.  
Coulda been dangerous.