Originally Posted by
ChipS
It is very possible that the IP trigger housing is original to your S'G' carbine. Saginaw Steering Gear of GM Corp. took over the Irwin-Pedersen (IP) carbine contract and plant in Grand Rapids, MI. Saginaw (S'G' designates the Grand Rapids works) also aquired all of the existing IP parts on hand at the time of takeover and used them, along with newly manufactured S'G' marked parts, during (mostly early) carbine production. It is very common to see an S'G' marked carbine with many IP marked parts, and vice versa to some extent.
Your hammer (B/R?) is probably a Rock-ola hammer and I don't know if Rock-ola provided any hammers to Saginaw S'G' through lateral transfer of parts, which was not uncommon at the time. Better informed collectors here may jump in on the hammer issue. HTH