(a) Preference categories
Subject to the conditions and provisions of this chapter and to any valid intervening rights acquired under the laws of the United States, any mining claim located under the mining laws of the United States subsequent to July 31, 1939, and prior to February 10, 1954, on lands of the United States, which at the time of location were—

(1) included in a permit or lease issued under the mineral leasing laws; or

(2) covered by an application or offer for a permit or lease which had been filed under the mineral leasing laws; or

(3) known to be valuable for minerals subject to disposition under the mineral leasing laws,

shall be effective to the same extent in all respects as if such lands at the time of location, and at all times thereafter, had not been so included or covered or known: Provided, however, That, in order to be entitled to the benefits of this chapter, the owner of any such mining claim located prior to January 1, 1953, must have posted and filed for record, within the time allowed by the provisions of chapter 11 of this title, an amended notice of location as to such mining claim, stating that such notice was filed pursuant to the provisions of said chapter 11 and for the purpose of obtaining the benefits thereof: And provided further, That in order to obtain the benefits of this chapter, the owner of any such mining claim located subsequent to December 31, 1952, and prior to February 10, 1954, not later than one hundred and twenty days after August 13, 1954, must post on such claim in the manner required for posting notice of location of mining claims and file for record in the office where the notice or certificate of location of such claim is of record an amended notice of location for such claim, stating that such notice is filed pursuant to the provisions of this chapter and for the purpose of obtaining the benefits thereof and, within said one hundred and twenty day period, if such owner shall have filed a uranium lease application as to the tract covered by such mining claim, must file with the Atomic Energy Commission a withdrawal of such uranium lease application or, if a uranium lease shall have issued pursuant thereto, a release of such lease, and must record a notice of the filing of such withdrawal or release in the county office wherein such notice or certificate of location shall have been filed for record.

(b) Labor and improvements
Labor performed or improvements made after the original location of and upon or for the benefit of any mining claim which shall be entitled to the benefits of this chapter under the provisions of subsection (a) of this section, shall be recognized as applicable to such mining claim for all purposes to the same extent as if the validity of such mining claim were in no respect dependent upon the provisions of this chapter.

(c) Withdrawal or reservation of lands
As to any land covered by any mining claim which is entitled to the benefits of this chapter under the provisions of subsection (a) of this section, any withdrawal or reservation of lands made after the original location of such mining claim is hereby modified and amended so that the effect thereof upon such mining claim shall be the same as if such mining claim had been located upon lands of the United States which, subsequent to July 31, 1939, and prior to the date of such withdrawal or reservation, were subject to location under the mining laws of the United States.