Translation request - Binoculars

[Mikemike88]

Hi
I've recently encountered some WW2-era Japanese binoculars with some faded kanji on the case. I think it's possibly a name. It's quite faded, but I would be grateful if anyone is able to make out what it says. Thank you.

 

[Toritoribe]

四一五艇
boat 415
(I'm not so confident with the second and third kanji.)

砲
artillery

 

[Mikemike88]

四一五艇
boat 415
(I'm not so confident with the second and third kanji.)

砲
artillery

Super. That's makes sense. Some.of the markings on the binoculars themselves indicate that they are
1) Artillery issue
2) have a marking for which the meaning is unknown but which is normally seen on navel issue binoculars.

Thanks for this.