6887 - Ysart Bros (Vasart) quite likely, but could be earlier??
6888 - The central cane and those in the circle around it are known in some pre-war shape IE bottles. This does not mean the stopper is one of those, but it might be.
6889 - No idea. Never seen that cane before. I'd like to see a view of the side of the canes.
In fact, I'd like to see full side views of the whole of each stopper. There can sometimes be clues (or a point of interest) in the way the stem is finished.
Also, could you please give the dimensions of each stopper, both the diameter of the top and the overall length from top to base of stem. There are a range of bottles, of "unknown maker" status, that use old "Ysart" canes but the UV check of the main glass and various other features do not tie up with early pieces.
The "unknown" items usually have larger stoppers than seen in regular Vasart bottles and Monart IE bottles. But there are also a range of (likely) older Vasart bottles, with clear necks instead of striped, that are larger the the usual ones!
More images and sizes would therefore be very useful in considering these stoppers.