SELECT
    rb.OFFICE_ID,
    rb.BINDER_NO,
    rb.BINDER_ID
FROM dbo.REV_BINDERS AS rb
WHERE
    rb.BINDER_NO IN
    (
        SELECT
            rb.BINDER_NO 
        FROM dbo.REV_BINDERS AS rb 
        GROUP BY 
            rb.BINDER_NO
        HAVING
            COUNT_BIG(*) = 1
    );

+-----------+-----------+-----------+
| OFFICE_ID | BINDER_NO | BINDER_ID |
+-----------+-----------+-----------+
|   2105110 |       108 |         5 |
|   2101110 |       106 |       265 |
+-----------+-----------+-----------+

SELECT
    OFFICE_ID = MAX(t.OFFICE_ID),
    BINDER_ID = MAX(t.BINDER_ID),
    t.BINDER_NO
FROM 
(
    SELECT
        rb.*,
        rn = ROW_NUMBER() OVER (
            PARTITION BY rb.BINDER_NO 
            ORDER BY rb.BINDER_NO)
    FROM dbo.REV_BINDERS AS rb
) AS t
GROUP BY
    t.BINDER_NO
HAVING
    MAX(t.rn) = 1;

+-----------+-----------+-----------+
| OFFICE_ID | BINDER_NO | BINDER_ID |
+-----------+-----------+-----------+
|   2101110 |       106 |       265 |
|   2105110 |       108 |         5 |
+-----------+-----------+-----------+

CREATE TABLE [REV_BINDERS](
[OFFICE_ID] [int] NOT NULL,
[BINDER_ID] [int] NOT NULL,
[BINDER_NO] [varchar](7) NULL,
);
go

INSERT INTO [REV_BINDERS] 
([OFFICE_ID],[BINDER_ID],[BINDER_NO])
select 2105110 , 1	,0101 union all
select 2105110	,2	,0102	union all
select 2105110	,3	,0103	union all
select 2105110	,4	,0104	union all
select 2105110	,5	,0108	union all
select 2105110	,6	,0105	union all
select 2101110	,261	,0101	union all
select 2101110	,262	,0102	union all
select 2101110	,263	,0103	union all
select 2101110	,264	,0104	union all
select 2101110	,265	,0106	union all
select 2101110	,266	,0105;

go

with emp as (
select
    OFFICE_ID,
    BINDER_ID,
    BINDER_NO,
    count(*) over (PARTITION BY BINDER_NO) as BinderCnt
from
    REV_BINDERS )
select * from emp where BinderCnt = 1;

go

drop table [REV_BINDERS];
go