If my effort a picture posting worked what you are seeing is a Ruger Red Label, a old model 20 ga, that has been converted to 45-70.
Had it done last year by a smith in Iowa. He's working on a conversion of a FN 16 ga to a RIFLED 20 ga for me right now.
The Red Label is PLENTY strong as are most shotguns of relatively modern manufacture. I'm no expert but it's safe so long as you don't go using loads that are rated for the Ruger #1 in the conversion.
And do be sure he proofs it properly! Better to blow it up while in the process than in the field.