Legras did use the mark shown on the two examples on ebay. I can not attest to the authenticity of those pieces.
I do not believe the "Leg" mark was used after WWI. I am not 100% sure of this, but the research I have done has indicated that the "Leg." mark was used on enameled pieces when the company was Legras & Cie. After WWI they merged with Pantin Glass Works to form Verreries et Cristalleries de St Denis et Pantin Réunies. At this point I believe they continued to use the full "Legras" signature on some pieces through the 20's & 30's. I am not sure the use of the "Leg," signature continued after the merge, but I do not know for sure.
Attached is an example of the signature on a different style piece that I know to be authentic. The style of enamel work this piece would tend to make me believe they used the mark after WWI, possibly into the late 20's or early 30's, which is what this design strikes me as...
Craig