House built in the 1890's. Floors seem to be in decent shape...Few decent scratches throughout. I can live with a few Dings here and there.

Screen and Re-coat or Sand down to wood and re-coat?

Hoping to get away with a Buff and a coat! Hoping it will remove the old finish and smoothen out the floor for new coats of Water based Poly.

Does anyone have any idea what kind of wood this may be?

Thanks guys!

Pics here : http://s613.photobucket.com/user/bfazio1030/library/

A careful re-coating over old varnish worked very well for the floors in my 1906 house in San Jose. It looks like you have vertical grain Douglas fir flooring, which came with very long strips, in the day. I cleaned with a low suds detergent then rinsed, but never screened, because the floor had never been sanded and the floor was not flat since only the sharp edges had been scraped smooth and sanded by hand. Since it took lots of work to get the preparation done, I hand sanded the whole floor with 150 grit paper, I decided to apply two coats of finish. It's been over ten years and the floors have an even gloss, still. If you spend the time to put on one coat which will seal any bare areas, there may be lower sheen where the wood was bare. The second coat will make it all the same gloss level. There is no advantage to sanding off any of the old finish if the new will stick to it. Try a small sample area in a corner after your prep work.
Our floor was the sub-floor, too. This means that there will be deflection in between floor joists. Near the front door where there was a lot of traffic there was a separation of the finish where the boards came together resulting in a white line between the strips. This is called "white line syndrome". This can happen with water-based poly-urethane, especially. The finish wants to bridge between floor planks and then breaks apart when stressed by foot traffic, or seasonal expansion/contraction.
To keep the effect from spreading I blocked the flooring from underneath by gluing strips of ½ inch plywood, ripped to two inch strips, underneath, between the floor joists. The strips were held in place with inch and an eighth sheet rock screws until the sub-floor adhesive cured. It comes in a caulking tube.
You may not need to do this if you have a sub-floor under your fir floor, but if you don't have a sub-floor this will make a big difference in how the floor lasts.
The materials that were available when old growth forests were being harvested for the first time are special and very expensive to replace, so restoring this floor is restoring a treasure.