unknown Sheaffer Skripsert (Lady?) model

[jos]

I recently acquired this Sheaffer which looks like a clipless Sheaffer Skripsert Lady but what it makes peculiar is that it is a Touchdown instead of cartridge filler:

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LS3.jpg LS4.JPG

I thought that the Sheaffer Skripsert Lady came as a cartridge pen only. Also the wavy line pattern is not shown in the Sheaffer Skripsert Lady reference list at Sheaffertarga.com (www.sheaffertarga.com).

The nib and cap lip are both marked "Sheaffer's".

Are there Sheaffer Skripsert experts out there that can identify this model?