as my main area of interest is mostly clear cut glass, I'm one of those who experience 'disappointment' due to the lack of available printed matter with which to attempt to id my pieces - though I'm not particularly biased or clever toward W.C., and take only a general interest in the stuff.
In my opinion, both your pix in this instance are adequate - though appreciate your comments that the max. size of first dimension of 700 is a tad restrictive, and I have been on other forums where 2000 is the norm. But we have to live with what we have.
Your image of the backstamp has the potential to be improved ……………….
try dusting it with talc slightly to highlight the appearance - or try carbon paper rubbed over the backstamp to darken it.
If you have a camera with magnifying properties, try running up the scale to increase the size of what is seen in the final picture - alternatively, use a loupe of c. X5, placed between the camera and subject - this will have the same effect and increases the size of subject seen within the picture frame. For backstamps in particular, raking light is often best - the light hits the part of the glass you want to photograph but doesn't create excessive glare.
It all takes a little juggling, but is worth the effort, and is more necessary with clear glass than coloured - in my opinion. Photograph pieces against plain dark backgrounds with diffused light - it's not difficult but makes all the difference, and don't show us pix of your furniture, garden, car, pets or the neighbours

I'd suggest a camera will be the better option rather than using a phone.
We don't appear to see much oldish cut W.C. glass here - Stuart, Thomas Webb seem more popular - something about Webb Corbett seems not to attract the collectors for whatever reason. Best of luck.