Its a 3-48, The only replacement I could find was -part #446-001-348 3-48 Raybar Shotgun Sight
www.brownells.com Hope this helps. Tony
6-48 TPI Remington/Ithaca/SKB
5-40 TPI Mossberg
3-56 TPI Browning Target Citori, Beretta, Kreigoff, Ruger, Weatherby, Winchester, Marlin, Stevens 311, H&R
M3.0-.5 Browning Gold, Citori Field, Franchi, H&K, Fabarm
M3-.6 Browning Citori Hunter
5-44 TPI Browning BPS
M2.5-.45 S&W
3-48 TPI New England Firearms
M2-6 will interchange with a 3-56 TPI