Since you have been to the LVA and Southampton you probably have seen some of these records. As I said I transcribed the first 900 entries in the Free Negro Register for Southampton. This covers the time period 1794 to 1812 It begins in 1974 and continues to 1860's..

There are no CROCKER's listed. However there are 5 entries for TANN

entry no: 91 Thomas TANN, 24, no race given, 5.7 1/2, Freeborn, Ston, day registered 1794 Nov 28

entry no: 93 Abram or Abram TAN, 38, Black, 5.6/emancipated by Henry Turner by Will, Soton, registered: 1794 Nov 29

entry no. 96: John TAN, 26, no race given, 5.6 3/4, Freeborn, Soton, 1795 Jan 6

entry no. 115 John Tann, Jr.?, 31, Mulatto, 5.7, Freeborn, Soton, 28 June 1797

entry no. 140 John Tann, 33/no race given, 5.7, Freeborn, Soton, 18 April 1800 (see 115)

I also did a search for any ISHAM as a first name:
Isham or Isham PRITLOW, 21, Yellow Black, 5.4, Nansemond, emancipated by Jacob Randolph, Josh Pritlow & Jas Deman, 1794 June 14.

I also looked at material for 2 adjoining counties..there was quite a bit of movement.

I took a look at the Sussex County register but didn't see anyone with those surnames.

I also looked at the Surry County VA REgister.......there were 3 CROCKER marriages from the Freedmen's Bureau Cohab List: Dinah, Joseph, Washington.

From the register:

Willam TAN, a Mulatto man and sonof Jammima Tan a white woman late of this county - he is bright complexion, has straight and black hair, pretty stout and straight made, age 21 last Sept. - Registered 3rd day of Dec. 1801

Selma