lets do it with displacement: go to photoshop and draw what you want to engrave on a 500X500 white backgroud, black painting. filters blur, gaussian blur (2 or 3 pixels) save it as normal jpg, high quality.

Back to maya window>rendering editors>multilister. Hit rmb edit create, lambert. double click the lambert swatch, on topmost place of the the window that gets open (atribute editor) youll find that you can swap betwwen lambert and lambertSG, hit lambertSG. the third atribute on the lambertSG sheet is "displacement mat." hit the chequered box on its side, on the create render node window that opens hit file, on the topmost of the attribute editor youll see displacement shader-file1, hit file1. On the image name filed hit the folder icon on its right, browse the image you created and open it.

If it is a planar and nothing weird happened before the image will be placed just on the center and it will renderthe cap a lil bit higher but the drawing on the original spot...

if not:
connect the file to the color of the lambert to make sure it is well placed( experiment with texture placing if it doesnt appears on the center)
the texture its well placed but the damn thingie doesnt displaces... dont panic:select the geometry of the cap and look the attribute editor theres a place called displacement map, hit the triangle and hit the calculate bounding box, render again, if it didnt worked higher the samples, if that doesnt worked keep experimenting