Ron Guth: The 1805 Small 5 Stems Half Cent is a very scarce to rare variety made up of two underlying die varieties: Cohen 2 and Cohen 3, both of which share the same obverse but slightly different reverses.
The nomenclature used for 1805 Half Cents can be confusing. The Small 5 is indeed small but the Large 5 is actually a normal-sized 5. It is only "large" relative to the Small 5. Perhaps the easiest way to tell them apart is by comparing the distance of the 5 relative to the bust. On the Small 5, the 5 is well away from the bust; on the "Large" 5, the tip of the 5 is close to the bust.
No 1805 Small 5, Stems Half Cents are known above Extremely Fine. Most examples have problems of one sort or another: porous planchets, scratches, dings, marks, etc. Nice, problem-free examples are among the scarcest of all Half Cent varieties.
Sources and/or recommended reading:
"American Half Cents, Second Edition" by Roger S. Cohen, Jr.