This is a closed cut valley (picture is from the wrong angle and not close enough to be 100% sure) or maybe a california.
The concern here is none, this is an acceptable means of installation and it is not recommended that metal be installed prior to the shingles, however it is recommended that ice & water shield or a roll product is installed on the deck prior to the installation of the valley detail.
The details for this installation can be see at www.certainteed.com if you care to see it. The type of shingle you will look under will be called Landmark.
I will point out that one post noted that the shingles must underlap at least 8 inches, the spec is that they carry over not less than 12 inches and nailing in the valley must be kept out about the same.
Problems to look for with any valley is leaking of course, look also for poor workmanship which should have you look closer as you may find that the parts that are not readily visivle will be installed improperly too.
The shingle in the picture is a Certainteed Landmark in the color Colonial Slate, the product could be a 25 or 40 year product and is likely to be 5 years old or older. The black shadow highlights on the cap shingles and the field shingles are distinctive to this product
Note, with the type of shingle pictured, architectural/dimensional, call out when the valley is installed with a full weave! problems can occur when installed using the full weave and the factory spec’s recommend against this method