Seems that mirrors is a deep subject Yamaha almost always had them off for the brochure shots so it's hard to ID what mirror is "right" for any model.
I think those black "beauties" were mainly seen on the XS750's. Most of my 74-79 standards came with round stainless mirrors.
Per the ever questionable parts fiches;
LH
This Yamaha 256-26290-10-00 MIRROR ASY LH is used on these models and components:
1970 XS1 HANDLE - WIRE
1971 XS1B HANDLE - WIRE
1972 XS2 HANDLE - WIRE
1973 TX650 HANDLE - WIRE
1974 TX650A STEERING HANDLE CABLE TX650A - XS650B
1975 XS650B STEERING HANDLE CABLE TX650A - XS650B
1976 XS650C STEERING HANDLE CABLE XS650C
PRODUCT OBSOLETE
This Yamaha 256-26290-00-00 MIRROR ASY RH is used on these models and components:
1970 XS1 HANDLE - WIRE
1971 XS1B HANDLE - WIRE
1972 XS2 HANDLE - WIRE
1973 TX650 HANDLE - WIRE
1974 TX650A STEERING HANDLE CABLE TX650A - XS650B
1975 XS650B STEERING HANDLE CABLE TX650A - XS650B
1976 XS650C STEERING HANDLE CABLE XS650C
BUT; the early 70-72 usually have clamp on style mirrors not threaded into the clutch and brake brackets.
I suspect the dealer set up guy just grabbed two from the "mirror tub" and bolted them on.
I think those black "beauties" were mainly seen on the XS750's. Most of my 74-79 standards came with round stainless mirrors.
Per the ever questionable parts fiches;
LH
This Yamaha 256-26290-10-00 MIRROR ASY LH is used on these models and components:
1970 XS1 HANDLE - WIRE
1971 XS1B HANDLE - WIRE
1972 XS2 HANDLE - WIRE
1973 TX650 HANDLE - WIRE
1974 TX650A STEERING HANDLE CABLE TX650A - XS650B
1975 XS650B STEERING HANDLE CABLE TX650A - XS650B
1976 XS650C STEERING HANDLE CABLE XS650C
PRODUCT OBSOLETE
This Yamaha 256-26290-00-00 MIRROR ASY RH is used on these models and components:
1970 XS1 HANDLE - WIRE
1971 XS1B HANDLE - WIRE
1972 XS2 HANDLE - WIRE
1973 TX650 HANDLE - WIRE
1974 TX650A STEERING HANDLE CABLE TX650A - XS650B
1975 XS650B STEERING HANDLE CABLE TX650A - XS650B
1976 XS650C STEERING HANDLE CABLE XS650C
BUT; the early 70-72 usually have clamp on style mirrors not threaded into the clutch and brake brackets.
I suspect the dealer set up guy just grabbed two from the "mirror tub" and bolted them on.