A young sporophyte is covered by a what seems to be a little hat, called the calyptra. (Technically, the calyptra isn't part of the sporophyte, as it actually consists of maternal gametophyte tissue, a remnant of the egg-containing archegonium.) The calyptra protects the sporangium (capsule) from drying out as it develops. If you're lucky enough to have calyptrae (a mixed blessing, since at this early stage in development the generally more useful peristome isn't available yet) its shape and size can be helpful. 

  
    

It's not the simple presence or absence of stomates that is diagnostic; it's whether they occur level with the uppermost cell layer (in which case the stomates are "superficial" ) or instead are sunk in a crater-like pit formed by the surrounding cells (immersed stomata). Like the procedure for checking cell papillae, stomate position is best detected by slowly focussing down, and noting whether the stomate and surrounding cells become sharp simultaneously (showing the stomate to be superficial) or instead the stomate snaps into view long afterwards (immersed).

stomate, static view

stomate, 7-step focus animation series

This moss has sunken stomates, additional evidence that it is an Orthotrichum (although a few of the less comon OH species do have have superficial stomata). Additional details about the stomates and the leaves reveal this to be O. pussilum.