Raimey,
If you had to make a call- would you say this gun is an XXIX ( in Sauer terminology) that was exported to the US and "labeled" whatever model designation by the importer as per their listed catalogue at the time ( 1923/24), or just a stouter optioned XVII ?
Perhaps another retailer ( were there any others importing Sauer guns at that time other than V,L&D and S,D&G?) ordered the gun and it was manufactured in a "lot" guns destined for US export?
Thank you,
Best regards
JBP