The provisions of section 6101 of title 41 shall not apply to purchases by the Forest Service of (1) materials to be tested or upon which experiments are to be made or (2) special devices, test models, or parts thereof, to be used (a) for experimentation to determine their suitability for or adaptability to accomplishment of the work for which designed or (b) in the designing or developing of new equipment: Provided, That not to exceed $50,000 may be expended in any one fiscal year pursuant to this authority and not to exceed $10,000 on any one item or purchase.