I just went thru the cabinet and measured Flues models as follows:
Model/gauge , ser #, Width at BF, Firing Pins CTC, FrameWidth@Breech , Forend Iron Width
Flues 20ga, #182974 , 2.013 , 0.968 , 1.382 , 1.370
Flues 20ga, #208430 , 2.070 , 1.041 , 1.373 , 1.315
Flues 20ga, #280972 , 1.903 , 0.977 , 1.366 , 1.332
Flues 12ga, #182124 , 2.355 , 1.121 , 1.498 , 1.438
Flues 12ga, #202500 , 2.410 , 1.187 , 1.496 , 1.422
Flues 12ga, #358962 , 2.333 , 1.155 , 1.448 , 1.425
Flues 12ga, #377767 , 2.315 , 1.121 , 1.453 , 1.411
Somewhere between Ser# 208k and 280K the forend latch and barrel lug were changed from a "J" spring to a sliding latch so if you attempt barrel swaps keep that in mind also.
John
28 Ithaca's and counting.
