This is a Starfleet Tricorder model TR-580 (circa 2369), with the medical option available as an attachment. I made my own custom stickers for this model, as stacking LEGO plates did not look very well.
About this creation
The tricorder has a hinge so that it can fully open and close. Better view (less blurry).
View of the front sticker, and the attachment points for the medical scanner. It attaches to the two outer divots in the technic piece on the bottom row.
The three basic piece of the tricorder. Top, bottom, and medical attachment.
Here's the whole thing put together.
This shows how the medical attachment is removed.
There is a wheel attachment on the inside of the medical module which the medical scanner attaches to.