U-BOAT U-51 Chimera - Watch Tool

[981as 9]

Hello,

I was wondering how to replace the battery on these, I assume the top 5 screws need to be opened, any idea where to get this tool please.

Thanks

 

[BravoDelta 22,442]

Harbor Freight maybe. A square bit set. 

https://www.harborfreight.com/security-bit-set-with-case-100-pc-68457.html

 

[981as 9]

thanks would the bit need to go into the deep square hole to turn it, or will it turn from the top shallow square.