Here's one: Pocket Folding Squares - Lee Valley Tools I have a Swanson like these that's an 8 inch and these might be Swanson's because they look the same. They are extremely accurate and you get the 2 different 45s included.

 

Swanson and Stanly...
smaller increments are on MACHINIST squares...

 

When I need measurements that small and from an edge I tend to grab my laser cut ruler

INCRA Precision T-Rules | Rockler Woodworking and Hardware

I don't try to use a square for small or precision measurements.

Charley

 

I use the Incra rule in the 6 inch version. It seems best suited for me. The 3" was small and the 12" was over kill for me.

 

I have a 12" Starrett precision rule. One side is 1/10s and 1/100s the other side is 1/32nds and 1/64ths. But each edge is different so I can choose the 1/32" edge if I don't need more precision.

I've had the rule for 30 or 40 years. I bought it when I was doing technical illustration and needed that kind of precision.

I have a 3" machinist square (no measurement marks) for squaring up saw blades etc.

 

I have a very old 12 inch Stanley that I recently cleaned up. Had it half a century, and it had a few miles on it when a family friend and carpenter gave it to me, along with an old 13 oz finish hammer. I also have a starret 6 inc and 18 inch, which are new and pretty good. I find myself using the 6 inch fairly often for marking for crosscuts. Just handier. The old stanley is very accurate and reminds me of the guy who gave it to me. He died when I was about 25, and he used to take us boys camping and for two summers, I was his apprentice on finish carpentry jobs. He also built 4 of my mom's apartments, which gave me even more exposure to construction. Funny how things can bring up so many memories.

At any rate, accurate marking also requires using some kind of blade to make the mark, and it also requires "sneaking" up on the mark. And for interior parts, that's what story sticks are for. The picture is of the knife I use. It has a flat side so your mark is righ on the line of a straight edge.

 

Tom bought a marking knife similar to yours from Lee Valley last year. They are nice.

Last night I bought a 4" Swanson square on Ebay. Stick said they were pretty good.