The SP-/SPE-Grade "Fox Special" was introduced in Savage's June 21, 1932, Fox retail and wholesale price lists. Early SP-/SPE-Grade guns had absolutely plain blued receivers. The March 1, 1934, price lists added a "Fox Special" Skeet Grade with straight grip, beavertail and skeet boring. For 1935 the SP-/SPE-Grade got a bit of engraving, and the Skeet Grade became the SP-/SPE-Grade Skeet & Upland Game Gun with quite a bit of scroll engraving.
Savage apparently had more of these flat-sided receiver forgings than they could sell as SP-/SPE-Grade guns, so made up some batches of flat-sided Fox-Sterlingworths.