Count duplicates and duplicates with suffix as one instance

Hi Ford
I copied your solution to my spreadsheet but the results aren't producing what I need, see attached file.

Because the weld on the same drawing number, no matter how many times it appears, counts as one weld--even if it's been repaired or cut out.

Hope that clarifies it better :-)

How's this...
On drawing 100789-D-G01 weld 01 has been completed but for whatever reason has been duplicated four times in a list. As far as I'm concerned this is one weld.

Same for drawing 1692-SG-0018-03. Weld 15 was completed and also repaired. The repair is noted as 15R1. These are both one weld.

And again for drawing 1692-SG-0040-04. Weld 05 was completed and repaired twice (05R1 and 05R2). All these are one weld.

For drawing 1698-SG-0047-02 weld 01 was cut out. This is noted as 01C1 and this is also classed as one weld.

On the rare occasion a cut weld may be repaired. So (making up a drawing number that's not in my spreadsheet) drawing 1698-SG-0013-02 weld 01 cut once and repaired once will be noted as 01C1R1.

I'm thinking if there was a way to look at cell contents for the two characters immediately to the right of _ and compare that with contents of the next cell down. If they're the same then 0, otherwise 1.

I've been going over this for days and it's doing my head in

I think I've found the answer!

=IF(LEFT(A2,FIND("_",A2)+2)=LEFT(A3,FIND("_",A3)+2),0,1)

On reviewing the data I need to verify a few drawing and weld numbers e.g. 100789-D-G01_01 vs 100-789-D-G01_01 but for the most part the results are what I'm looking for.