Picture number two

[GOPHER SLAYER]

The year was 1873.

[Tatume]

The year was 1873.

The model is 1873. The year is not indicated.

[Scharfschuetze]

The only model numbers that you'll generally see on Trapdoor breech blocks are:

1868 (50/70)
1870 (50/70)
1873: from 1873 up to the Model of 1884
1878: This is a miss stamp and if looked at closely, you'll see it was supposed to be 1873. I think that it is attributable to a bad stamp at Springfield Armory. I've seen a few of these and I believe (without checking) that one of my 1873 rifles is so marked.
1881: 20 gauge "Forager" shotgun
1884: This is on both the Models of 1884 and 1888

Back when the Springfield Trapdoor was in use, unit armorers probably mixed and matched parts to keep weapons functional. I have seen Model 1888 Ramrod Bayonet rifles with 1873 marked breech blocks and I'm sure that there are other examples out there.

To check the actual date of the receiver's manufacture, you'll need to compare your serial number to the production records. There are several charts available on-line and in various publications.