Does anyone know if the Ray-Vin '03 Springfield Sight Micrometer can be used w/ Krag? See below link. 

According to the web page, it can be used w/ the Trapdoor Buffington sight, but there is no mention about the Krag rear sight.

If it it ,can't anyone know of some one making such a tool??

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Yes it will work on the Krag 1901 sight.

Ray, they have raised their price quite a bit lately. I noted an ORIGINAL went by on E-BAY last week for 56.00. Just dirty but would clean easily.
Also check GUNBROKER I have seen them there also.

They will work on your Winchester Winder Musket too.

The O'Hare mikes are nice tools and I wish I had one myself, but it's a measuring device only on anything but a rifle with the sight radius it was designed for.  Probably much more portable and easier to use than my Dial caliper.  Ones I have seen are a nice fit inside the staff. I looked up there site and a real good set of instructions come with the O'Hare that mention you need to record the settings for different distances and loads as well as individual rifles.

I guess it depends on how you are going to use the Micrometer.  For our Schuetzen matches shooting without a coach and lots of time we only need precision.

Across the course shooting military rifles the way it used to be done shooter will dial in sight settings as directed by the coach so easy ways to add 2 moa or take off a couple of minutes is a key requirement. 

When I used to shoot Military matches in the Reserve often times we did not even set our own sights. Rifle was handed to you set and told to shoot it don't worry about the strike.  Gunners Mate would then change you sight to suit what he saw in the  spotting scope. Objective was for the team to win and they did not want a bunch of hard heads twisting on the sight knobs. These were M1's altered to .308. Thinking back could see the usefulness of the O'Hare if 03's Bet they were used the same way.

On Step blocks these are good dodges too.  I used to have one of the H&R Officers model Trapdoors. Tang rear sight with no graduations.  I zeroed then cut a piece of brass  that fit inside the staff at the correct height plus a little.

Back at the range with a file cut the block down trying it at 200 yards until it zeroed perfect.  This for a Swinger gong match always at 200 yards.  However it was a fair amount of trouble.  Next match noticed one of the Trapdoor shooters doing essentially the same thing with his dial caliper. And he only had to note the reading in his notebook not do all that filing for just one pre set distance.

Boats

P. J. O'Hare was the preeminent maker of this type of tool in the U.S., selling them mostly to the High Power competitors.  Of course there were other manufacturers, but on a smaller scale than O'Hare.

David Kaiser
Montezuma, IA

Boats,

Those are late 19th century ones - some for Long Lees, others for Martini's. Ventometer?  from latin, meaning wind (wind in french is also 'vent').   
These were for use with the MBL class rifles (miitary breechloaders)  - graduated to give MOA adjustment, and for windage, you were supposed to draw a line on your sight blade with the appropriate correction so you knew where to hold.
BTW - as to US/UK names - there's a few that are the same, but have a different meaning...  like 'broad' 

Yes,

These do have a vernier scale - which for elevation is actually marked on the knob, seems to be quite accurate.  You can find them with the 'big' names on it - I have one marked 'Jeffereys'.  However, I do believe these ventometers are typically British - never saw a continental one.  Sometimes you can even find an add-on set of match  sightsfor military rifles, FWIW.