Scott's 900 was a privately raised New York Cavalry Regiment and had duty in Washington, DC in 1862. It would appear many soldiers would join the 11th New York Cavalry later on.

From a newspaper.

SCOTT'S 900.—We have received a letter from an officer of Scott's 900, dated Camp Relief, Washington, March 9th, which informs us that the officers have received their commissions, bearing date March 1st, from Gov. Seymour. The men have also received their State bounty. The regiment is destined for the Gulf Department, and the last detachment will probably leave this week.
The following is the list of officers:
Colonel—J. H. Sherburne, A. A. G. of Gen. Martindale's Staff.
Lieut. Col.—S. H. Wilkeson.
Majors—S. P. Remington, J. C. Kenyon and G. W. Richardson.
Company A—Captain, vacant; 1st Lieut. E. C. Hand (commanding); 2d Lieut. C. J. Bronberg.
Company B—Captain A. G. Campbell; 1st Lieut., A. B. Holmes; 2d Lieut., A. Hazleton.
Company C—Captain, E. D. Benedict; 1st Lieut., Geo. A. Bagwell; 2d Lieut., ____ Skinner.
Company D—Captain, J. B. Mix (detached); lst Lieut., G. Nicholetts (commanding); 2d Lieut, — McKenzie.
Company E—Captain, J. C. Hyatt; 1st Lieut., J. C. Burgess; 2d Lieut., ____ Von Wiltzein.
Company F—Captain, M. A. McCallum; 1st Lieut., ____ Raymond; 2d Lieut., G. D. Demison.
Company G—Captain, H. B. Ellsworth; 1st Lieut., R. P. Goodale; 2d Lieut., T. W. Allen.
Company H—Captain, Thomas T. Gamble (detached); 1st Lieut., J. S. Bennett (commanding); 2d Lieut., C. B. Gibson.
Company I—Captain, J. F. Slawson (detached); 1st Lieut, R. Littleworth (commanding); 2d Lieut., J. Johnson.
Company K—Captain F. B. Halleck; 1st Lieut, vacant; 2d Lieut., H. French.
Company L—Captain, G. W. Smith (detached); 1st Lieut., J. R. Wood (commanding); 2d Lieut., vacant.
Company M—Captain, J. Norris; 1st Lieut., H. C. Bates (detached); 2d Lieut., D. Massey