I looked into SRM-1871 to SRM-1875 at
https://www.nist.gov/srm. They have all been discontinued and are out-of-stock. The certificates can be viewed here:
https://www.evernote.com/shard/s23/sh/15b5752e-cc21-7ffa-76bb-5f899dfe78bf/db6a20766a2b0eff03b30baeaa187191. They consist of glasses engineered by Doug Blackburn and D. Kauffman numbered (K456, K493, K523), (K453, K491, K968), (K458, K489, K963), (K495, K490, K546) and (K496, K499, K1013). I believe that both Blackburn and Kauffman were long gone by the time I arrived at NIST in 2004. It is possible that some of these glasses remain in a drawer somewhere. I'll look around. Alternatively, a microanalysis standard vendor might have shards they might sell. As for a contact, I'm probably about as good as it gets. The original contacts have all retired.
Here is the compositional data I have on the K373-K377 glasses (except K374 for which I have no data)
NIST GLASS K 373
CATION NUMBER ANION NUMBER WT PCT COMPOUND WT PCT ELEMENT AT PCT ELEMENT
Na 11 2 8 1 14.06 10.4304 10.3462
Si 14 1 8 2 68.13 31.8484 25.8555
Zn 30 1 8 1 6.15 4.9407 1.7236
Ba 56 1 8 1 11.59 10.3803 1.7241
U 92 3 8 8 0.063 0.0534 0.0051
AVERAGE ATOMIC NUMBER 22.4626
WEIGHT PERCENT OXIDE TOTAL 99.993
WEIGHT PERCENT ELEMENT TOTAL 99.993
ATOMIC PERCENT ELEMENT TOTAL 100
WEIGHT PERCENT OXYGEN 42.3397
ATOM PERCENT OXYGEN 60.3455
NIST GLASS K 375
CATION NUMBER ANION NUMBER WT PCT COMPOUND WT PCT ELEMENT AT PCT ELEMENT
Na 11 2 8 1 14.05 10.423 10.3429
Si 14 1 8 2 68.09 31.8297 25.8506
Zn 30 1 8 1 6.15 4.9407 1.7242
Ba 56 1 8 1 11.58 10.3714 1.7233
U 92 3 8 8 0.13 0.1102 0.0106
AVERAGE ATOMIC NUMBER 22.5302
WEIGHT PERCENT OXIDE TOTAL 100
WEIGHT PERCENT ELEMENT TOTAL 100
ATOMIC PERCENT ELEMENT TOTAL 100
WEIGHT PERCENT OXYGEN 42.3249
ATOM PERCENT OXYGEN 60.3484
NIST GLASS K 376
CATION NUMBER ANION NUMBER WT PCT COMPOUND WT PCT ELEMENT AT PCT ELEMENT
Na 11 2 8 1 13.99 10.3785 10.3367
Si 14 1 8 2 67.72 31.6568 25.8049
Zn 30 1 8 1 6.12 4.9166 1.7222
Ba 56 1 8 1 11.54 10.3356 1.7237
U 92 3 8 8 0.63 0.5342 0.0514
AVERAGE ATOMIC NUMBER 23.0501
WEIGHT PERCENT OXIDE TOTAL 100
WEIGHT PERCENT ELEMENT TOTAL 100
ATOMIC PERCENT ELEMENT TOTAL 100
WEIGHT PERCENT OXYGEN 42.1783
ATOM PERCENT OXYGEN 60.3611
NIST GLASS K 377
CATION NUMBER ANION NUMBER WT PCT COMPOUND WT PCT ELEMENT AT PCT ELEMENT
Na 11 2 8 1 13.91 10.3192 10.3237
Si 14 1 8 2 67.28 31.4511 25.7523
Zn 30 1 8 1 6.08 4.8845 1.7186
Ba 56 1 8 1 11.47 10.2729 1.7209
U 92 3 8 8 1.26 1.0685 0.1033
AVERAGE ATOMIC NUMBER 23.6903
WEIGHT PERCENT OXIDE TOTAL 100
WEIGHT PERCENT ELEMENT TOTAL 100
ATOMIC PERCENT ELEMENT TOTAL 100
WEIGHT PERCENT OXYGEN 42.004
ATOM PERCENT OXYGEN 60.3812