plz help identify signiture on Okimono

[RUBENSAN]

HI,

I've got this beautiful Okomono, at least 50 years in my family. wanted to know about the signiture. Thank you!

[Bugyotsuji]

The remains of three price stickers I see!

 

The dark dyed signature seal looks as if it was added later, following along some of the ivory cracks. For this reason my gut feeling is that any reading will not help us at all. Ready to be proved wrong of course! 
 

Good luck with your project. It’ll be interesting to see what others say.

[Matsunoki]

As Piers suggests…….
“Signature” is not a Japanese one. Crudely carved and awkwardly orientated. 

The underside is not finished to Japanese standards.

Can we see the okimono please?

I feel this could be Mammoth tusk.

[SteveM]

The square inscription that looks like a seal reads 大明成化 (Dai ming sei ka), or, if you use the Chinese pronunciation Da ming cheng hua, alluding to Chinese emperor Chenghua (mid-1400s)

 

It's apparently a motif that was used by Japanese ceramic artisans to give their wares an air of antiquity and authenticity. I think used by Imari porcelain artisans in the late 1800s. 

[RUBENSAN]

Thank you guys! here's the okimono from both sides:

[Matsunoki]

Yep, it is Chinese. 
Well outside of my knowledge!

Looks old but the Chinese are masters of ageing things including ivory.