2 1/4" X 2 3/8" (54mm X 58mm)

No markings 

{No inner skirt}

Picture courtesy Bob Berry

2 1/4" X 2 3/8" (54mm X 58mm)

No markings 

{No inner skirt}

Picture courtesy Dave Dangora

2 1/4" X 2 3/8" (54mm X 58mm)

No markings 

{base view} 

Picture courtesy Dave Dangora