You're correct, a serial number that low would be a 1907, even the 1917's in 380 with a trailing letter started higher than that. You're sure it's a 1917 with trapezoid grips rather than the rectangular gripped 1907? Hard to guess at much more without a picture.
Here's a picture. The two on the upper left are 1907's with rectangular grips. Two on the lower left are 1915's with rectangular grips and a palm safety. Top 2 in the second from left row are 1917's with trapezoid grips.
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